Hey, thanks for the update, it's nice to see you're moving along on your project.

-4l60E: If it's out, it might be easier to just take it to a shop and have a shift kit put in, however , i think the stock one will hold up just fine until you get everything done and the truck running. Plus the tranny doesn't need to be removed to install a kit.
-Driveshaft: I've had three of them blow up due to critical speed, my final shaft is made by denny's driveshaft and it's held up fine, lots of money, but no more headaches.
-Radiator: You should be able to use the stock rad, of course like he said above, a v8 rad. will work, i went with a Howe Radiator, www.alumrad.com
-Ignition: Your stock on will be fine, at the most some NGk's and some aftermarket wires.
-Tuning: try www.nelsonperformance.com hahaha, thanks for the business
-Intake: stock airbox with a custom air tube and kn filter, that should work and look nice and stock under the hood,
-Fuel: stock lines will work just fine, just cut the GM ends off and use some rubber line to tap into the fuel rail. Not sure if you're using the truck intake or LS1????????The fuel pump won't cut it, buy an aftermarket 255lpg pump and it will go right in place of the other one. You need 60psi.
-If you go with some tuning, I can turn that off, Veh. Anti Theft Sys.
-Rails would look nice

-Exhasut: I have the 40delta flows and my truck is quiet during idle and normal driving.
-Get the tranny cooler, b&m is the best, the others suck, just from exp.
-Gears will get you through the isntall, do those later, unless you can afford it.
-I removed my ac bracket and ac, i didn't like how much power it pulled, i'm going to pull my engine and cut and box the frame so it's in the stock location.

With this setup you'll be running fast and getting over 20mpg,

Great Project,

allen