I'm still not catching on to what you are trying to say, but no big deal. Either way you go, the 7.4, or staying with the current 5.7, you can't go wrong. It the end it just comes down to preference, what works for you, and how big of a wallet you've got.
I saw you mentioned you have a Z71, that does make a difference as well in weight and etc. Where as I was talking about my 2WD, which is considerably lighter (without diving too far in, I am less a transfer case, another driveshaft, heavier rear, and front axles), not mention I have a stepside bed, which is primarily fiberglass and has less area than an 8' fleetside, let alone a short box. Which then puts our trucks into two different categories that you cannot truly compare fairly.
First, I will not need heavier springs in the front, as I have done a similar swap with a heavier engine into a lighter truck using the same springs as a '96, and it sat, handled, and wore tires exactly like it should, therefore I am assuming (from past success) that I will not have to. (Long story short, '84 SWB GMC, broke a spring, pulled used ones from a '96 at a scrapyard. Then put a Pontiac 400/TH375 into it, replacing the 305/TH350 that I had a lot of fun blowing up) Pontiac engines are heavier than Chevy's, yet still manage to beat them cube for cube. At least, all of MY Pontiacs have never seen a Chevy's taillights.
But I digress, back to topic. Since 2WDs were the discussion starters, we will stick with that. Starting with curb weight differences in an everyday ECSB Fleetside and ECSB Stepside (I gathered a few weights from different sites and averaged them, to be fair)
Stepside - Approx 4600lbs (bare, no driver, toolbox, sound system, etc)
Fleetside - Approx 4800lbs (same)
And I'd like to point out that I had already factored the difference of weight in transmissions in my initial argument as well (since that was mentioned as an add-on in your rebuttal). So, about a 200lb difference between SS and FS, give or take. If you remember, the difference between the 350/4L60E and 454/4L80E was approx 207 lbs. Just by having the Stepside, I am already ahead in the weight game, as I am now approximately the same as a Fleetside, and am putting out more power at lower RPMs (which is what you want in a street vehicle).
Now, since I am the one who is doing the swap and explaining why I have nothing weight-wise to worry about, I will use my truck as an example. A jobsite that I visit weekly has a scale (for incoming freight) and I decided to weigh my truck about two weeks ago, just out of curiosity. It weighed 4,300 lbs without me in it, so with me its 4,520.
Things to consider when I weighed it -
1/2 tank of gas
Aluminum toolbox with very little in it besides basic sockets and hand tools (I had just cleaned it out)
Bucket seats with no center console. Originally had a 60/40 bench
New carpet (you would really be surprised how damn heavy your stock carpet is, damn near knocked me over as I pulled it out replacing it)
No bedliner (it takes about 3 gallons to do it yourself, more if it's done professionally. Go lift a gallon next time you're at the parts store and tell me that doesn't matter)
Clutch fan and shroud removed
CAI (if you have one pick it up in one hand and your stock intake in the other, there's quite a difference)
No hitch
Overload springs removed
And other little odds and ends. So, now when I put my 454 in - which will weigh even less than the argued weight of 945lbs due to headers instead of manifolds, removal of smog equipment, injector swap (pick up a Multec and an LS1 injector, the Multecs are much heavier), and removal of the clutch fan - my truck will STILL weigh less, or maybe the same as, a bone stock Stepside.
My point is, EVERY little bitty thing you do adds up. Or subtracts, depending on what you're doing. Next time you're changing something, compare the difference in your hands, you may be surprised. Something as simple as a radio, my JVC I installed was considerably lighter than my factory unit. My electric fan is MUCH lighter than the clutch fan and does a much better job. Those damn overload springs are surprisingly heavy for what they are. However, when I installed my drop hangers, they were heavier than the stock ones. My steel SS wheels are heavier than the factory aluminum ones (I'm swapping those out too in exchange for aftermarket aluminums, so there's MORE weight gone!).
I guess my whole point is, the "big block will make your truck weigh more so it's not worth it" generalization is inaccurate and very misinformed, since everyone's truck (or any vehicle for that matter) and setup is different.
The same with the "big blocks cost more" generalization as well. Which, granted, is true more often, but is still not a concrete argument. My case in point being that I have started and abandoned the big block route twice before my current attempt, (primarily due to insufficient time more than funds) and have never lost money (in fact, made quite a nice profit both times) after selling the parts off or spent more than I would have on the small block to get the same output.
Back to the Pontiac topic I started earlier, I am working on using a factory L29 harness and PCM to run MPFI and a 4L80E with a Pontiac big block. Then THAT will be what ultimately goes into my truck.
I'm sorry I can't go into more detail, I would really like to and do have much more to input. But my kiddo is hungry, and I just can't deny a hungry little boy his pizza.
