Balance it on a trolley jack, sitting at 45 deg with the propshaft flange raised. Gradually lift the trolley jack while feeding the flange over the chassis crossmember (appropriately protected). As you raise it you can level it off. I think I loosely fitted the two lower bolts and then the long top bolt with a long screwdriver inserted and wiggled to get the bolt in. Probably a lot easier if you didn't have to do it on your own on your back in about 2 ft space. You'll get it eventually, just before you lose the power of your arms. What bit are you struggling with? I found getting it off far harder, getting the suspension bolts off, the drive shafts out and, especially, the long top bolt out.