tbi conversion questions?

[lofly'a]

i am in the starting stages of putting together a 454 for my 71 GMC swb and, planning on using feeding it with a tbi setup. here's what i have so far, a 1976 454 (haven't checked specs yet), a complete tbi setup from a 91 ck truck,
and a 91 454 throttle body from a 454SS.

my questions so far are, can i use the 91 harness, ecm, etc..... do a chip change and use the 454 throttle body? how much can i modify the internals of the engine (cam specs) without going outside of the ecm/tbi's control? i'm hoping for 300 to 325 hp which i'm told is conservative and do-able. i've also looked into Xtremefi's 750 cfm throttle body vs the stock 420 cfm unit and have been assured that the Xtremefi unit will operate properly, and support this build. My only other plans besides what mentioned are long-tube headers/exhaust, and a hotter spark.

I would appreciate all chime-ins and advice i can get.