The 8100 is a whole different animal than a 454. It's a clean sheet design that basically uses the same dimensions. Different crank, different firing order, different heads, etc.
For mostly driving around town, I definitely prefer the driveability of the 8100 over the diesel. I'd have to tow a heavy load pretty frequently before I'd prefer the diesel. (And yes, I've driven both VERY extensively, since several years before they went into production.)
