vibration at 25-40 mph

When you loosen the big bolt to align the small holes, tighten the two tranny bolts first. This will allow the mount to rotate, and then you can secure the large bolt,locking it all in place.The little bolts have; large,thick,rectangular "washers", and bolts with integral loc-washers on them. All this to prevent them from working loose. Be careful to replace them with correct length bolts.