Man, I've been down this road.
At the end of the racing season last year, I started having problems skipping right over 2nd gear with the slapstick shifter. Thought the shifter was shot. Replaced it with two differnt shifters... Console in-out-in-out.
Same problem. Finally noticed my oil pan was resting on the steering linkage. What the?
Turns out the mounts were shot. Right sided really sagged down and left side sagged down and broken. I have a torque strap, so it wasn't really noticeable.
I wanted to race the following weekend so I just got a cheap set from the local parts store. Went to the track twice and the new mounts were shot. Sagging again and back to shifting problems. I guess the shifter linkage was getting out of alignment somehow and/or rubbing on the header at the collector.
So I got the Polylock mounts from Schumacher. When I called, they were on back-order and I had to wait a little over a week before they shipped, but initially they said it could have been almost a month delay.
The Polylock mounts do not sag at all and created clearance problems with my Hooker Supercomp headers and the torsionbar on the left side. Thankfully the headers are two piece and I just removed the rear tube and clearanced it for the torsionbar.
I was surprised at all the vibration the polylocks DO put into the car.
My engine is balanced, but isn't exactly stock either.
I have nine passes and not sure how many street miles on the poly mounts with no signs of trouble.