[NorCalAnthony]

Nice swap! I’m gathering up parts to do the same thing to my ’89 K5 and there’s a ton of good info in this forum.

Some things that I don’t see on your list:
-VSS signal: A couple of companies make an in-line pulse generator so you can keep your stock transfer case but I’ve heard mixed reviews on them. I was lucky and found a np241c out of a 90 Suburban that is still a passenger drop but has the VSS built in.
-Fuel Pump: The fuel pump on the newer truck is usually an assembly so if you plan on using it you’ll need to get a fuel tank adapter like the one that Vette Works sells. Not sure if you can remove that pump from the assembly and switch it straight over like the EP381 pump from a late 90’s truck that most people use or not. Another possible issue with using the newer sending unit is it won’t work with your stock fuel gauge but if you’re going to aftermarket gauges that won’t matter…
-Fuel tank: You may want to look in to swapping in a tank from an 87-91 Blazer/Suburban with the baffles in it otherwise you may run in to fuel starving problems when the tank gets low and starts sloshing around.
-Radiator Hose: Most people just use the stock radiator with the upper hose from the donor vehicle.
-Steam line: Some radiators have a threaded plug below the upper radiator hose outlet that you can screw in a barbed fitting and run it from there. Another option is a coupling with a barbed nipple that you can install in the upper radiator hose. I forget who makes it but I’ll see if I can find the link when I get home.
-Transmission: It may be easier/cheaper to just find a 4x4 trans than to try and build one from the two you already have. From what I understand, it has to be taken almost completely down for the conversion which adds a lot to the cost if you’re having a shop do it. If you’re wanting to up the power level on your engine you’ll probably want to them add a shift kit and a Corvette servo while they’re at it since those trannies have a hard time keeping up with even just the stock engines. It should basically be the same size as your 700r4 and should drop right in without needing new shafts.
-4.8 vs 5.3: If you already have the 4.8 I personally wouldn’t bother trying to convert it to a 5.3, it’s not worth the time, trouble, and cost of the parts for the little power difference you’ll gain. If you do decide to go that route, you can have the 4.8 pistons put on the 5.3 rods to get you a decent compression bump. If you’re wanting to get up to 350 rwhp I’d look at picking up some used 799/243 heads, a TBSS intake, and a custom spec’d camshaft without a crazy intake and duration or you’ll shift the power band too high for a heavy 4x4 truck.
-Smog: You may want to check and see what specifically the smog laws in your area say doing an engine swap. Out here in Cali they’re pretty ridiculous and require that you swap over all of emissions items (cats, egr, o2’s, etc, the entire evap system, and the matching newer transmission supposedly because that’s how it was configured when the it was certified by the EPA or whoever... The smog ref will also hook up to the OBD II port and make sure that everything is functioning properly before they’ll sign you off. I was able to pick up a complete wrecked donor so I have everything I need but most guys out here don’t even bother with the hassle. Hopefully you don’t have to worry about any of that stuff out in Colorado though.