First and foremost, I've already nit-picked a few previous posts regarding basic upgrades, but most also involve a newer-gen swap of sorts as well which, aside from transmission, I'm not necessarily trying to do. Yet.

I just got a neglected '87 IROC-Z, manual transmission. It runs, but overheats like a MF, so for all intents and purposes it's not road-worthy. Already getting that worked on though.

The reason for a fresh post is because of how specific my question is: how do I get the most out of its original setup/350 with TPI? 350-400 HP range
(I'm well aware manual third-gens came with 305's, but this one's been swapped with a 350. No other changes have been made.)
The engine will need replacing because it "clacks" after a while, so it's only a matter of time, hence why I won't F with it on the road.
My plan is to replace it with a new 350 (or 383, but I heard that entangles significant work being fuel injected). Before dropping it in, I wanna get as much out of it as I can.
To give y'all a ballpark of what I want out of it:
*NOT trying to race it/compete/blah blah blah
*Also don't care about how economical it is on fuel
*All I want is for it to be quick out in the street, and have SOME sort of resemblance to a muscle car, not just a "gets me where I need to be" drive
*I WILL be replacing the tranny with a T56, but that's another forum (as are brakes, etc. anything else requiring mods to keep up with said upgrade). Wanna keep this forum engine related, but thankful to be pointed in the right direction regarding the rest 🙏🏼

Of note: I'm a newbie in automechanics, so to answer potential questions regarding what else is in it now, it's all original. Being a newbie is also why I wanna take a stab at DIY and feel like sticking to a new replacement 350 to modify will be simpler than, say, jumping to an LS swap. One bridge at a time!
I live in Tri-Cities, WA so if anyone knows of a reputable engine/tranny shop in the region, let me know. Thank you!

 

Rebuild it. If stock crank checks out ok can reuse it. Throw in a good flat top piston and rod package. Bore .030 to clean up cyl, good ring pack in it

that should get compression back up. Need a budget set of heads for it. New intake manifold if wanting to keep it efi and make power. Sell the stock tpi stuff if its tpi. Then a mild cam like a 224/230 and its good to go.

not cheap to do, will need chip tuning. Or go aftermarket efi system like holley hp efi or equal

 

This reply is prefaced by your budget considerations as well as who is going to do the work:


If keeping it "original" (how it looks under the hood) isn't a concern for you, sell the TPI, and go with either a carburetor---or better---an aftermarket user- programmable FI unit on top of a 383. You can get the extra cubes---and the extra hp/torque that comes with them---for not a lot more $$$ than a 355 rebuild.




^^^These mods will be a requirement based on the engine upgrade.

 

TPI isn't really going to get you there; the long narrow runners boost low speed torque and sacrifice top end flow, which is where you'll be making the 350-400hp number. TPI does have stellar power production below 3000rpm, which is desirable for a street car, it's just going to struggle to make over 300hp regardless of what you do. So, do you like the characteristics of the way the car is now, or would you rather have something that rips up higher in the rpms to make power?