I took a measurement of the one spot I can reach. Spacer is just under an inch. Plate is 1/4 inch. So it's a tiny bit under 1 1/4" total. I'm guessing bolts would be around 1 3/4". They are metric from memory, maybe 10mm. No aluminum bolts. Only standard bolts I came across are transmission bellhouse. Was a little tricky bolting the mount to the plate.

The way I came up with the height was I matched the v6. I left the 904 in and kept the Trans at the same height. I think some people raise the engine to get more clearance.