thanks for the info guys - ran the tests on the booster and pump from the service manual last night, and its definitely the pump and not the booster that's my problem. my pep boys has the vacuum pump in stock as well as the stock tensioner, so i can do the work this weekend. after researching the SD tensioner mod, though, i'll see if i can pick that up instead. ...and see if they'll take my spare stock belt back and swap me for a new longer one for the mod.

in related news, Talyn's post confused me for a few minutes, before i realized i had mixed up the crank pulley and water pump pulley in my head. my water pump pulley is fine. its my crank pulley that is wobbling. hopefully its just a loose pulley and not shot main bearings... i guess we'll find out this weekend.