These pics were taken awhile back and I wasn't planning on doing a writeup with them, so please excuse the poor photography, I just took them for documentation originally
Stock 350 part # is 7213, it will be on a sticker with a barcode on the front side
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Stock 454 is 6144, this way you can easily identify them if they're not on an engine. The 454 TB also has a taller air horn (the very top ring where the TB hat sits), a flat throttle blade, and a larger IAC valve opening
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Disassemble both of them, though you can't see it very well (sorry), the 454 throttle shaft is on the right, and has a slightly different design than the 350/305 one (left). The little rings you see at the ends of the shafts are the retaining rings I mentioned in the original post, I used a 3lb sledge with a shop rag to buffer so that I didn't mushroom the shaft. I used firm strikes, and took my time. Don't rush it.
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There is a bearing pressed in behind the TPS, you will not need to remove it, but don't damage it
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I highly recommend a thorough cleaning. I used a sandblaster (if you dont feel like repolishing the inside, tape it off before you blast it or just use B-12 carb cleaner to clean it instead, that's good stuff)
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Now, the parts you will need - 454 main body and throttle plate, 350 throttle shaft and return spring (the 454 spring is too soft, the truck will idle too high). The TPS and IAC are the same, so it's your call on that one.
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Reassembly is simple. Slide the shaft back in (don't forget the throttle spring), you can put the retaining ring back (I didn't on my final assembly, the first one I did I used a 10 or 11mm socket to drive it back on). Slide the throttle plate back into place and screw it down, and put your sensors back on. Viola!
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There is a couple of differences externally. The 454 body does not have the throttle cable bracket bolt hole on the front. I just left it unbolted, hasn't affected anything. The air horn is also taller, which means the hat won't just slide back on. I had to remove the riveted on piece that clamps under the lip and just use the retaining nut to hold it down. Again, have not had any issues from that. You could also trim down the air horn so that it will fit properly. If your truck idles high after the install, unplug the TPS and IAC. It will idle down, then just plug them back in (your CEL will illuminate, but will go back off after a couple cycles). The only thing I have noticed concerning that is that occasionally it idles a little high at startup for a few seconds longer than normal, but doesn't last long.
I hope this helped. From now on I'll take better and more pics so that I can explain things properly.