There's vibration coming thru my shifter at 3200+ rpm. I think it could be my flywheel. Can I figure out what flywheel I need without taking it out first?
It depends. If you are near stock and will remain that way there isn't much benefit. If you plan to make a lot of power and race it then the SFI rating of most billet flywheels is a plus. If you plan to make big power and run a metalic friction clutch disc then you need a billet steel flywheel as the iron will fail quickly when matched with that type of friction material. Most billet wheels are a few lbs lighter too than the iron wheels.
I'm just wondering how the flywheel could go bad and cause vibes. There's no weight that can shift is there? I think the imbalance is built in. Might wanna check into other possibilities.
Driveshafts and harmonic balancers are a lot easier to check and replace than the flywheel. If the driveshaft is mis-aligned/unbalanced then you will definitely feel the vibration in the shifter. Put it in neutral and rev the engine. If you still feel it in the shifter, it's not the driveshaft. Check the balancer for rubber protruding anywhere around its edges.
If you recently had a clutch install done and the flywheel wasn't balanced correctly then you're about to have a pile of fun.