I have a 351C with FMX transmission, 8 inch 3.55 gears in the rear end. I pulled this transmission and driveshaft that had a 351C and 8 inch rear end as well from a 72 Mustang Coupe and it is now in in a 73 Mach 1 Fastback. I installed the drive shaft tonight and it is sitting front and rear on car dollies. I do have extended shackles on the rear (3 hole type, using the middle hole. Can't remember the amount of lift the 2nd hole gives to raising the rear end). With the driveshaft fully installed, I have about 1 1/2 inch of space that if the rear of the driveshaft were disconnected, I could probably move it all the way forward 1 1/2 inches although I did not check that. The drive shaft is engaging because I put the trans in Park and the driveshaft would only rotate a little bit, in Neutral, it would rotate. My question is: is this too much space for travel or am I good to go. I have read that you need about 3/4 of an inch for travel but I have double that. Thanks for any response and assistance.
Tom
Tom