The mounts appear to be for the "adapter kit" and if I am seeing Butler's pictures correctly, the mounts are wider apart and would make sense as to the longer bolt.
Don't know what frame mounts you have installed from what year? That may be where the issue is?
If they fit the block, and drop into the frame mounts, then they should be good to go. Use your shorter mounting through bolt and go with it. Poly will be stiffer/harder than rubber, so not as bad as a solid, but not as cushy as a factory rubber mount. Some like to mix/match using the poly on the drivers/torque side and rubber on the passenger side. The engine limiter can be a good idea on bigger HP engines, clutch cars, with good traction tires.
If all else fails, call Butler.
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