I'm in a similar situation (5.3 into an '88 Supra), but something I haven't seen addressed is the wiring harness when using a later (2003 in my case) 5.3 with a cable TB & the LS1 style injectors- I have a damaged wiring harness that came with the motor. My motor still has the electronic TB that I can't use, and the injector plugs are different than the 42LB injectors I want to run. I just bought a 1998 LS1 harness to try out & see if this is more adaptable than the LM7 one.

EDIT
I found out the trucks use Multec-2 type injectors, and the cars use Bosch style. The plugs & bodies of the injectors are different, but with some work they can be swapped.

I'm looking for an LS1 F-body oil pan & related items, and have bought an LS1 manifold, TB & rails and am shopping for injectors.

I did, and I plan to add a single turbo @ 6-8 PSI with a front mount intercooler.