Just to add another angle to this (no pun intended).....i have the kiesler tko 600 in my 68 b body on the street, and my goid friend runs one in his 71 E body. In both cases, we each have viabration issues at higher speeds. His being much worse than mine. Mine starts at about 75 mph and higher. I chased this around and have all new parts. I have checked bith cars, and in each case, the transmission is installed almost touching the tunnel. We cannot get the rear of the transmission any higher and this causes the trans to driveshaft angle to be less than optimal. It is pointing downward quite a bit. This is also the case in his car. Pinion angle is off and this has been causing a viabration. In order to set the rear angle equal and opposite, the rear would have to be setup pointing up like 6 degrees. We both race around the streets and that is asking for trouble with yokes and ujoints for us. So, we just live with it. The kit could have been more thoroughly engineered with proper dr shaft angles in mind. My opinion.
Maybe this is the cause of viabration he has. Have him check his trans, driveshaft, rear angles.
You need to shim the rear axle between the spring and the housing to get the correct driveshaft angle. Drive shaft angles depend on the alignment of the centerlines of the pinion shaft and the center line of the motor/trans. What that relationship may look like from under the car makes no difference. it sounds to me like the front of the motor is sitting too high, which is causing your vibration issues. If you can't raise the tail of the trans high enough to get the correct drive shaft angles, you have to rotate your rear axle to get the correct numbers. You will also have to modify any traction additives accordingly.
As it is now, you are getting the vibration because you are trying to bend the driveshaft every 1/2 revolution. When the driveshaft angles are correct, and the traction assistants are adjusted correctly for the "new" rear axle position, everything will play much better together. Gene
