i have a 1972 220 and im trying to put in a motor form a few years later, im trying to finish a project my dad started before he died. how do i figure out what motor mounts i would need and where can i get them

 

From your description, you have W115 or 115.010 chassis car and original engine was M115 or 115.920. If it is a diesel, then you have 220D model W115 or 115.110 chassis with 615.912 diesel engine. Now you have to tell us what is the model of your replacement engine (should be stamped on it) or what chassis and year it came out of.
This reference may help you out a little.
http://www.adsitco.com/reference/