The 85 f. pump gives you more psi range, helps to get proper throttle response b/c if you port or swap manifolds, you'll get more air. the increased f. press. will help in tuning. The vortec 350s in 96 up trucks were rated around 265h.p. I think adding the vortec heads & tbi intake will get you to about that. The C4s have a much better exhaust than those trucks. Ussually a vortec head swap is good for 40h.p. The beauty of those heads are the low lift flow #s, which means they'll flow alot better even if you reuse you cam, or go upto 1.6 rockers.
Another thing about these manifolds is they make power through to 6000rpms. And you could probably put a 383 in it w/out alot of trouble. There would be more power avliable w/ tuning.
The cam I would choose would be discussed w/ a cam manufacturer, like COMP & Crane. They'll ask you about your car (eng. size, efi, trannie, rear gears, ect.) then tell them what kind of performance you want. Bigger & Badder isn't always the best way, cause the idle might be rough, or not enough low end torque, low engine vacuum.
This is what I did around 2001, Trick flow 23* heads, holley tbi intake, holley 670 tbi, & a Crane(?) extreme 4X4 cam. Ran really good &torquey, no tuning or check eng. lights.
Then in 04 I put in a crane retrofit roller cam, same specs as their tpi cams, roller rockers, acell ign. system , ceramic coated the exh. manifolds(1 of the best things you can do on a c4, really cut the temps down) & a smokey SY-1 intake. This intake gives up idle quality & alittle low speed torque for strong mid & top end power. My cam is good through 6500rpms so I can bury the tach easily. I have 3.07s now but this intake/cam combo really should have 3.73s. I have the stock converter in the trans, the rest of the exhaust is 1984. It seams to run good at 12 psi f. press. ign. timing is at 12*. The 84 f pump should make 12psi, but the volume it makes (like at wot) would be less, esp. on a modded motor. W/ coated manifolds, I don't think there is alot of hot air being sucked in the open air cleaner, really makes a loud noise at wot, like the old 4 barrels.
So the cam doesn't have to be changed, but cam tech has improved in 25 yrs. It's all about how much you want to spend.
I'd look on ebay for the heads, any vortec dual plane intake( tbi or carb), If you use a carb intake you'll need the tbi adapter, any tbi for a 87-89 p/up, throttle brackets, this should get you going good. If you go with a oem throttle body make sure you do the ult. tbi mods.
