Long Bed -----> Short Bed conversion questions

[Lazybones]

My truck is a Regular Cab Short Box 1500. I'm working on a frame off restoration (lots of rust in this area) and LS swap. There is an undamaged (and mostly rust free) frame for a 2500HD Regular Cab 8' Box for sale locally. I went to it twice with the idea of replacing my SB frame with the heavier RB frame. Most of you are aware, and I became aware after measuring twice, that the frame tapers from the same width at back of the cabs to the same width at the end of the frames. The SB frame tapers at a sharper angle than the RB frame so at the 6' point the RB frame is wider. I threw away my diagrams with actual dimensions but sketched up one to show visually the difference. Something as basic and simple as the rear SB box mounts would be in thin air because the RB frame is wider at that point. And that is just the beginning of dealing with the width difference problems. Add to that the spring purchase on the axle would not be the same width as a SB and not the same as a RB.
I hope this helps.

 

[1989GMCSIERRA]

I have searched the forum and google and haven't really found a good answer to 2 questions I have. I plan on moving the spring perches and chopping the rear off the frame. I want to keep the truck as original as I can as there's sentimental value there, so a frame swap is off the table. I'm even debating just cutting down the bed. Might be more work than it's worth. The wheel arches need a patch anyway, so I may just swap it with a clean SB.

I already have the small gas tank. Using this method, do I need to move the tank and crossmember forward or not? If not, what do I do about the filler neck?

Lastly, what do you do about the rear shock mounts?

Thanks for any help in advance.

That’s not how you shorten a long bed to short bed frame. Before you do anything please research what it takes to do a frame chop
I would go buy a short bed frame. As soon as you cut into the long bed frame it’s no longer original. Swapping the bed also kills the original part. I rather get a short bed truck complete and swap cabs than to bumble through cutting a frame to shorten it. If you have never done that

 

[evilunclegrimace]

My truck is a Regular Cab Short Box 1500. I'm working on a frame off restoration (lots of rust in this area) and LS swap. There is an undamaged (and mostly rust free) frame for a 2500HD Regular Cab 8' Box for sale locally. I went to it twice with the idea of replacing my SB frame with the heavier RB frame. Most of you are aware, and I became aware after measuring twice, that the frame tapers from the same width at back of the cabs to the same width at the end of the frames. The SB frame tapers at a sharper angle than the RB frame so at the 6' point the RB frame is wider. I threw away my diagrams with actual dimensions but sketched up one to show visually the difference. Something as basic and simple as the rear SB box mounts would be in thin air because the RB frame is wider at that point. And that is just the beginning of dealing with the width difference problems. Add to that the spring purchase on the axle would not be the same width as a SB and not the same as a RB.
I hope this helps.

This is going to start a pissing contest but, here goes.
The rear cross member that is X shaped is the same part number long or short bed.
The axle is the the same part number long/short bed.
The rear fuel tank cross member is the same part number long/short bed.
The springs are the same length long/short bed.
The rear bumper is the same part number long/short bed.
Now having said all of that, IF you position the rear spring hangers on a long bed chassis 14" foward and reposition the rear X shaped cross member the same distance as it would be on a short chassis the taper would be the same. The only issue MIGHT be the positioning of the front spring hangers. And yes you would have to move the shock mounts foward also.
Granted,It would be alot of work to cut all of the rivets, repostion all of the componets and drill and bolt them into place,in addition to drilling the top rail of the frame to match the bed mounting bolt positions. But that does not mean it cannot be done.

 

[Canadian Rust Bucket]

The only issue MIGHT be the positioning of the front spring hangers.

I could see that being a real headache. If you measure 14" forward of the current position of the spring hangar, you're halfway through the front bed mount. Did the short boxes have a different style spring hangar?

 

[Caman96]

This is going to start a pissing contest but, here goes.
The rear cross member that is X shaped is the same part number long or short bed.
The axle is the the same part number long/short bed.
The rear fuel tank cross member is the same part number long/short bed.
The springs are the same length long/short bed.
The rear bumper is the same part number long/short bed.
Now having said all of that, IF you position the rear spring hangers on a long bed chassis 14" foward and reposition the rear X shaped cross member the same distance as it would be on a short chassis the taper would be the same. The only issue MIGHT be the positioning of the front spring hangers. And yes you would have to move the shock mounts foward also.
Granted,It would be alot of work to cut all of the rivets, repostion all of the componets and drill and bolt them into place,in addition to drilling the top rail of the frame to match the bed mounting bolt positions. But that does not mean it cannot be done.

Agreed, pretty much anything can be done. But doing it right is another thing. There’s NO going back once the cutting starts. So many would love that truck as it is.

 

[evilunclegrimace]

I could see that being a real headache. If you measure 14" forward of the current position of the spring hangar, you're halfway through the front bed mount. Did the short boxes have a different style spring hangar?

I believe that they are the same short/long.

 

[evilunclegrimace]

Agreed, pretty much anything can be done. But doing it right is another thing. There’s NO going back once the cutting starts. So many would love that truck as it is.

I agree, It is a very nice truck but to each his own. I personally do not like trucks that are lowered and bagged but I think that everyone should do what they like.

 

[Caman96]

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[Cree]

Which frame is that? Or are you telling me they're the same and you Chevy did what I'm thinking of doing but in reverse?

 

[Caman96]

If I’m seeing it correctly, it’s showing all the wheelbases relative to each other. I marked the long bed and short bed. You can also see what lazybones was pointing out.