When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
All of the combos you mentioned have been tried. Figure out your goals and what driving characteristics you are willing to put up with - that will help you decide on either big cubes or stock cubes + FI.
I would wonder about longevity of the bottom end of the motor. To handle all the horsepower, once you change all the stock internals, you might be better off starting with a forged 427 C5R block.
There have been several threads in the FI C5 section on some sad souls who pushed the HP limits but used the stock differential and destroyed it.
But I believe a new one is only about $2K if you install it yourself.
My buddy did this... Head/cam package with intake, exhaust, etc... Then added a supercharger... LOTS OF POWER! Shredded his rear end at the track on his second pass on drag radials. Cost an additional $1800 with DIY labor... Lots of power to be made with the combo, just plan ahead for the azz end...