Driveshaft upgrade time

With all upgrades to engine/trans and deciding on which rearend to run I just about forgot about the stock driveshaft.

What kind are you guys running? I have the stock one w/7290 u joint upgrades, is this fine or will I twist it like a pretzel?

just a reminder: 500ci 650hp #3400 65 Coronet,727 w/3800 stall footbrake,no nitrous.

Is an aftermarket 3" fine or do I need to upgrade to a 3 1/2 or 4? Give me your opinion of Alum. Worth it or just a fancy waste of money.
Author: wedge5