TBI era is literally the worst starting point to upgrade, as everything but the 4 bolt block needs upgrading. Tiny heads, no compression, poor fuel injection, computer controlled ignition timing, terrible intake manifold, enough sensors required to make it annoying to wire up.
My 93 K2500 454 experience:
I did a comp cam SK11-302-4 212/218 and 911 springs upgrade, and I bent the pushrods. I thought it was a wiped cam, but it was just normal wear on the lifters on breakiin. Ran awesome. I have the cam and lifters in a box still. But too much lash. So I pulled it out and another cam. Wiped that cam for real on startup. So I pulled the engine and bumped the compression up with dome pistons and a comp 215/215 magnum roller cam to get away from flat tappets. Had to remove the rotators, I think that was my problem. The springs had the right installed height I think 1.9xx?, but I never verified the pressure, so I may have had too much spring for the flat tappet versions or it was bottoming out.
For injection, I went with Holley Sniper and hyperspark ignition. Sure it works, but lots of people complain about it but I suspect it is their lack of following the wiring instructions. I'd go with another Holley than the sniper if had to go that route again to get the Holley to also control the transmission, but those will run $3000-4000 by the time you buy everything. Right now I have the Holley for fuel/ignition and the stock computer hooked up to control the trans.
I like the 215/215 roller and stock gen V peanut ports (removed rotators and installed spacer/locaters and custom short poly locks to have an adjustable valve train with full roller rockers to fit under the stock valve covers). It is all done by 5000 rpm and starts falling off. Has tons of torque off idle. If I shift at 5000 1-2 it barks the rears. The factory shift point of 4200 or so is fine 99% of the time.
HYDRAULIC ROLLER: Daily driven street machines. Works with stock converters. Likes headers. 396 needs 3.55-3.73 gear. Very slight rough idle.
Holley Sniper EFI w/Hyperspark Weiand 8122WND intake 1 inch Phenolic carb spacer Comp Cams K11-302-4 212/218 .503/.503 on 112 FT Hyd Hooker super comp long tubes (torch and hammer time I'm sure) Plan is to wire the TPS and tach leads up and let the factory computer control the 4L80E. Got...