I didn't think about the torque ramifications. The cover for the clutch lever came today, there is no way it is going to fit. Im thinking I might have to invent my own cover. Im not sure I want to install a cable system, there's already to much stuff in the engine compartment with the Borgeson power steering hoses. If they went under the box like the original it would be less crowded in that area.

Good suggestions, I'll do that. The motor mounts are the stock grocery store, nothing fancy brand. So is the transmission mount. I had to drill the holes in it to move it so it would fit. The tail shaft wasn't in the center of the tunnel when I installed the trans mount. I loosened all the motor mount hardware and shoved it over to straighten it out. I ran a string down the driveshaft along the center of the engine. I looked straight.

There has always been a slight vibration in the car ever since I installed the C4. I've always thought it was the drive shaft balance but never perused it.
  I wonder why a CV wasn't used instead of a U-joint, then it wouldn't matter how straight it is. Same way with a wobble socket? Need some new inventing going on.

The '77-'80 Lincoln Versailles used a "double cardan CV joint" in the driveshaft at the rear end. Obviously NVH was a concern in Lincoln cars.

Sorry, I didn't mean to misslead anybody. The lug is the least of my worries, I don't think it will be an issue, but if it is, it's gone. My issue is the cover for the clutch lever. I haven't found one that will work or fit the combination that I have come up with using my original 1970 lever on the T-5 / SBF bellhousing. I decided to make my own cover fashioning it after a pocket door. My current battle today, besides broken airplanes, has been fitting the boot around the Pro 5.0 shifter. It's taken me most of the day but I think using a piece of Kiazen foam as a seal will be the ticket.

Drove the Mustang around the block tonight. I think it works good. It gently works it's way out of 5th and into neutral. I think the carpet might be doing that. The car isn't put together enough for hi-way driving to verify it.

I'll re check it. And the carpet.

This is how it finishes. I'm OK with it, it is a place to put the cell phone. Had to cut off the bottom of the hole so it would fit all the way down flush. I'll have to remove all that to re adjust the stop bolt on the pro 5.0. It still slips out of 5th gear. Seems like it has more power now. Must be the difference in gearing and rotating mass vs. the C-4. It is now obvious that the vibration is the engine. Couldn't isolate it before. I'm not sure what can be done about that.

75 MPH 2000 RPM. 3.0 limited slip. AFR 13.3 average. Doesn't lug in 5th till about 40 mph. It's a little slow to pick up speed at 70 mph to pass a car but was doing 95 by the time I got past him. No more exhaust resonating at any speed, seems quieter but I forgot to turn on the radio.

My RPM is about the same as yours in fuf gear. I usually down shift to 4 if I wanna 'git-on-around-'um...butt on the interstate I just make it happen in fuf (unless its a durned-old-shivel-lay) then I pass'em with much vigor! maybe even 3rd gear!
6sal6