Hi everyone,
Two issues if I may,
A). I get a very loud vibration and noise when I back off the throttle after doing about 70-80 mph, (3,000 -3,500 or so rpms. The U-joints are good, the center bearing and related parts are new, the trans mount is also good, and the rear end is also good. I did use sections of driveshaft from two different sources when putting in my od trans though. So...I am assuming that the driveshaft is not balanced. I took it out and re-aligned the two halves 180 degrees, but that just slightly changed the rpm and loudness of the vibration.
Am I correct it is the drive shaft? Is there something else I should check?
Is there any way to check or balance the shaft w/o taking it to a shop?

and...
B). I would like to put in a 164 motor mount as a trans. mount but when checking my tranny mount I noticed on the 142 that the holes for the bolt ends are smaller and there doesn't seem to be as much room. My thought is to drill out the bolt holes slightly and cut the mount bolts just a bit so it will fit, (with the bolt ends the 164 mount looks too long to fit between the trans and that folded end on the cross member). Has anyone done this?

any input, suggestions, or opinions?
Thank you,
Chris