i have an ud pulley intalled in my motor right now and i wanted to put either the stock one back on or an ati super damper. can i do this even though my engine was balanced when i rebuilt it??

 

Your underdrive pulley should be neutrally balanced, therefore replacing it with a neutrally balanced stock pulley will not change you engine balance.

 

how do i find out if mine is neutrally balanced. i forgot what the machine shop told me.

 

The safest way is to take it to a automotive machine shop and have the balance checked. The stock pulley has holes around the perimeter; see if there are any weights placed in any of the holes that might have been used to create an "offset" balance.