Can anyone here tell me what the differences are between a stock 330 hp 454 and the 365 hp 454 mag?

The 330 have two bolt mains, cast crank and pistons, small port heads and low cast iron intake.

The 365 have four bolt mains, 7/16" rods, forged crank and pistons, large port heads, hi-rise aluminium intake, different cam and CR.

Some call the 454 Mag 385hp. Did they dump it up when they went fuel injected?

The 365 was 1988ish thru 1991 or so.

Externally, the 365 has an aluminum high rise GM intake. It is painted black, but you can put a magnet to it and tell easily enough. That'll be your EASIEST tip off.