74 dart vibration problem.

A bent pully wouldn't make it vibrate unless it was bent alot. You said yourconverter had weights an you think it had a 360 in it at one time. There will be a small wieght on some 318 converters for balancing of the converter alone . But If you have two larger wieghts side by side it is for a externally balanced 360 or 73 . 340. Both weights can be removed while in the car. I have done this for guys.

They are spot welded on . You can take them off with a cut off wheel by carefully cutting down through the weld until you are close to the bottom and then chisel them off. I wouldn't suggest just trying to chisel them off without cutting through some of the weld first. I have seen guys pull a hole in the converter at the spot weld. Do this where a tig welder is handy incase of this happenning you can just tig weld it shut. Do not use a mig sometimes the wire can feed into the hole in the converter and cause it to bind.

I would say if you got weights this is your vibration. Most engine builders balance engines if combining parts from different motors. But they have no control over the converter used.