Don't forget, if you choose to build your current 454 as you mentioned, you will have to ditch the stock exhaust for something better flowing to notice any big difference. Many others have chimed in on this in other threads............plus I am currently building my 1990 454's and without changing exhaust will probably only get to around 375hp.
9.4 cr
049 heads
mildly upgraded cam (no reversion issues) 224duration .510lift 114lsa
edelbrock performer intake
match porting