Unless I missed something here, you have a stang wanting to do a sc engine. Use a mustang based t5 or better such 5 spd. Every 5spd owner hates their m5r2 and yearns for the day they will make a t5/borg warner/richmond compliant for it. Also, your shifter will sit about 6 inches further back if you use the m5r2, so get creative with a sallzaw or a jig, and start cutting. If anything, sell the m5r2 for about 300-500, assuming it's in great shape, sell off current tranny from car, then buy a better performance based t5, and then, launch at about 2500 if your on street tires, 4000 if on drag radials/slicks. Just my .02 of what i'd do. M5R2's are garbage when beaten on. They only used them because they would hold the torque of the engine.