350 Mag vs std Merc 350

Anyone have any idea on how to ID a 350 mag versus a standard Merc 350?
(or am I completely smoking crack?)
I'm looking at a Glastron that came with 3 options:
1) 305
2) 350
3) 350 Mag
I've got the 350 vs 305 via the casting number on the block, but can't distinguish between #2 and #3

they usually will say 350 magnum(sticker).
Another way look at the intake and carb hi rise and a weber carb(afb copy) vs a low standard intake and a qjet.