https://www.rx7club.com/2nd-generation-specific-1986-1992-17/interesting-vibration-speed-mounts-driveshaft-tires-671830/

The vibration referred to here...I think I found it.

I've ruled out driveshaft...it is very tight, not enough to cause any sort of vibration.

However, the bushing in this mount is...gone? 0.0



That's a pretty good way to cause a pedal specific vibration at highway speed.

Where can I get that bushing?

 

Home depot - get a few big washers.

Fixed.

 

its like $80 or something from mazda

 

anyone have a picture of the stock one I can see?

 

After looking at some other pictures, I'm having trouble knowing if this is the problem or not...anyone think it is?

 

I didn't read the other post to see what your problem was, but that mount is definately shot. The problem is actually the two upper mounts (y-blocks) that actually hold the weight. When they go bad the cause the tranny to sag and the lower crossmember looks like that. You will need to replace the y-blocks as well as the crossmember. If you only replace the crossmember the new one will soon look like that. I recommend getting the competition mounts from mazdatrix, it will run you about 140 or so for all those parts but it will be nice and stiff, but not crazy stiff like solid mounts. You might also invest in new engine mounts while you are at it since they are probably in similarly bad shape. Again, I recommend the comp mounts from mazdatrix.
http://mazdatrix.com/g3.htm