A Few Issues With My 518 Conversion??

I'm certainly no expert on transmission swaps etc. But.. as far as your trans not wanting to shift gears without letting off the throttle, unless you've had a shift kit installed in it, your kickdown just needs adjusting.For the vibration, if it gets worse the higher the engine rpms get, then it could be several things. Might be the flywheel/flexplate or even the torque converter, but also the trans mount. If it gets worse with higher speeds, I'd have the driveshaft looked at again. If it stays the same regardless of speed or RPM, then you may have a problem with the torque converter.