so why can you just swap the top over and call it good?
You can't topswap and call it good. You have to tune for it. Having the higher compression and Boost causes more heat, which causes detonation. Flow mods, cooler plugs, and cooler air (intercooler) and tuning, are all ways to fight the detonation, AKA knock.
1997 Grand prix GT Black Coupe- The beater
1998 Grand prix GT Black coupe- Top swapped, XP cam
2008 Grand prix Midnight blue- The slow but nice car
1999 Chevrolet Silverado red ext. Cab