I just finished the with the torq specs on my rebuild this weekend, more specifically checked all the engine mounts.

If you are looking at the front of the bike, there is roughly a 3/4'' spacer on the bolt for the frame sliders, and on the other side nothing.

However, I checked on my other race prepped bike and there is one, i dont think its stock but i went to ACE and brought in the bolt, which i think is 3/8 or maybe 5/8 cant remember, and bought a steel spacer that is 1/4'' thick, it fits like a gem on the left side mount to cover that extra space you are worried about.