Reading off the drawings in the books.
1970 the engine centre line as the datum
The dry frame is 16 7/8" from the datum to the centre off the lower steering head bearing plane
The swing arm centre is the datum line , this is approx 1.2 inches above the motor centre line, .
The 71 drawing shows datum to lower steering head plane centre is 13.643, adding 1.2 , gives 14.84, about 2 " lower than the dry frame? relative to the motor that is
never mind all that, I am sure it will all be fine, its been a popular upgrade for decades.