Sure it will - Wheres theres a will theres a way.
Now, if your talking oem stock mounts and so fourth thats another questions entirely.
First off I'm thinking you meant 455 and not 454 as thats a chevy motor.
I'm no pontiac man by no means but I figure if the regal in question came with 350/400 V8 then it should fit with minimal effort as the blocks outside dimesions are the exactly the same, so with that being said, yeah.
Cp