Headers hitting idler arm

Can either (or both) of you elaborate on the taller tranny mount? I was unaware that this was a possibility. I thought there was the crossmember that fit your car/transmission and that was that?

When I shimmed the engine on the Scamp, I used 3/16" plate and that gave me plenty of room. I agree that it wouldn't be wise to get carried away with shimming, so I think if I choose to go that route, making shims out of the same 3/16" stock would probably give me the room I need.

I guess the reason for posting here was that I was worried that something may have been wonky underneath and not simply normal fitment issues. I'll keep the thread updated as I make progress.
You already have it figured out but, yes, a plate between the mount and the transmission or even the mount to the cross member will accomplish the same goal. Just remember that this will change your drive line angle a bit.