[Cobra #3170]

I am pretty sure the clutch isn't slipping, it is an 8" Magnum force twin disk with metallic facings, the car can and did spin the tires yesterday at over 100 mph in third so I think the tires would give up before the clutch under any circumstances.

What I have found so far:

The drivers side Goodyear has 3/16" of radial run, out the passenger side is about 1/8.

The LH halfshaft is 180 degrees out of phase along its' length with the RH halfshaft, I know that the radial acceleration and deceleration will cancel through the system but it will be different along the length of the halfshaft, side to side perhaps I am getting a vibration from that difference at high torque levels.

The drive shaft looks OK for phasing but I need to really check it with a straight edge.

The rear end cradle studs are loose on the drivers side, it is always the passenger side that comes loose first because of torque reaction, this is the first time the drivers side has come loose. I will clean them and use green Loctite on the stud threads this time on all 4 studs.

That seems like an excessive amount of tire run out, no passenger car company would ever allow a tire like that on any of their vehicles.
God only knows what the force variation under load is. Many years ago while in the military I bought a set of recaps from the PX, they cost $10 each and had similar run out, that car shook like hell too.

I will check the flywheel tomorrow, along with all mounts for engine trans and diff as suggested by loading them.