Quick time makes the spacers I am wondering about. Wouldn't those be machined to a close enough tolerance to keep everhtning aligned? Tney make one. 375" thick that has engine mounts ala old time bellhousing mounts. Would it be an invitation to disaster to go with front of block and bellhousing mounts when using an aluminum bellhousing and T5? If you're block-mounted, it should be no issue. However, I would still caution you about spacing out a bellhousing due to input shaft alignment. This is a critical measurement requiring tolerances of <.005" and typically .002-.003" - if out of alignment, at best, you'll eat pilot bushings/bearings and at and 65-up patterns...and I too have never actually held an Astro/Safarii T5 in my hands....
The Jalopy Journal
