trans mount
No! Not unless you dont mind taking the chance of cracking your bell housing. If you are going with a poly trans mount you need to do the motor mounts at the same time because with just a poly trans mount the engine still torques over and the tranny doesnt move as much which puts a lot of added stress on the bell housing.
You probably wouldnt want to do that. People do it anyways but it puts all the stress on the back of the transmission. The motor mounts will still flex but the transmission mount wont budge much adding stress there. If you were going to use that I would also do the motor mounts the same way.