Driveshaft vibes

[David Head <dave.head@worldnet.att.net>]

After replacing the center bearing on the 200q with a 325 part and mig
welding the tangs on, I've got bad vibes - after a few attempts to shim
already. Worst is 28-38 mph, lesser at all speeds above.
Compounding the problem is the fact I can't say my mech marked
orientation on the driveshaft - meaning I could have a balance problem
in addition/instead.
Any tips/ideas? My only prior driveshaft balance expertise was a 66 GTO
Convt - it just got worse as speed got higher.

Dave
89 200q - Casper