Ok official disclaimer: I am not a mechanic, just a farmer building a hot rod! This is how I did mine, likely not correct way to do it. As I am old and fat I don’t like rolling around on floor. I installed engine with tranny bolted up snug, once installed I took a baseline dimension of tranny tail shaft, then jacked tranny up until I got a hard stop, trying to establish amount of play or droop I had in tranny travel. Then lowered tranny back down to unsupported position again, took another measurement to see if good base line was correct. Then I jacked tranny back up until it was relaxed and engine was not stressing motor mounts. Again shameless plug for Hemi Denny front ends, tranny was supported by jack at this point so that I could play with pitch. Everything felt and looked relaxed and unstressed. Make bracket to fit! Remember some spacer material so you can get bracket in and out. Feel free to PM me anytime and I can give you contact info if it helps you.