66/67 B body housing is about 1 1/2" longer than A body and perches are about 1 inch wider.
That means your wheels will be 3/4" further outboard each side.
You will barely notice the difference in the perch location.
Moderate pressure from one spring to the other and it will literally drop on.
There's one on Orlando craigslist right now for $150.
This is a SUPER EASY swap.
M body is 1/2 inch wider overall than 66/67 B and 1/2 wider perch distance.
Better fit and better axle to do 66/67 B.
