I have a 75 280Z and just spent 1 1/2 hours trying to remove the four bolts where the driveshaft connects to the differential. I had no luck because leverage and space was a problem. I don't remember this problem on my 74 260Z or 71 240Z. If I remember right on those two cars all I needed was two wrenches and off them came. Looking at the driveshaft it appears that the bolt head is prevented from turning by one flat of the bolt engaging a flat spot on the driveshaft flange. I sprayed rust lubricant and heated the nut side but my wrench started to round out the nut. The only other idea I could come up with was drilling through the bolt head side to weaken it and knocking it off with a chisel. I'm not worried about saving the hardware but I'm in a time crunch because I need to pull my engine/xmsn. In it's place will go a chevy 327/muncie 4 speed. Any other ideas anyone?