davidpozzi was correct in indicating that the difference between a 396 and a 427 is BORE and difference between 396/427 and 454 is BORE and STROKE.
My question is: Is the 454 and 396 block exactly the same (except crank for stroke)- i.e. is the 396 bored out less at the factory than the 454 (i.e. can I bore is to 4.251" like a 454 and beyond?)- or does the 396 have thinner cylinder walls than the 454 to start with?
To answer your ? No! You cannot bore a 396 out to a 454 size. As stated previously .060 is about the most that you can go. The blocks are the same with the exception of the bore of the cylinder when the cast was made. The walls will not allow for that much bore. If you wish to use the 454 crank and rods with the 396 block you can purchase a set of pistos with the corrocponding compression hieght and have a stroker 421 CI engine. I've seen it done. Just a little food for thought.
I had a .060 over 396 with stock type pistons, closed chambered heads, a good solid cam and a 750 dbl and open intake. I was able to walk away from the all-feared guy with the 427. They may not run quite as strong as a 454, but they are no slouch either. You have to think of winning as a package deal. Id consider going with the 396, since you have one, and using a taller gear. Good luck
The 396 is nothing to be sad about. I would be happy to have one. I used to build 454's all day long for boats, they are strong motors butthink of all those SS396 cars out there. They are still tough contenders.
Some early 396 blocks can be bored to 4.250"(454). Knock out the center freeze plug, and if a standard pincel will fit between the cylinders you can't do it. But if the pincel will not fit between the cylinders you can. You should always have a block sonic checked before boring it.