Aspen brakes on an A body.

the F, M,J and late B body spindle is 3/8" taller. It is an excellent upgrade to the old drum brakes on any A or B body. The 3/8" makes no significant difference in the geometry and will not "over angle" the upper balljoint. Do the math on the change in angle, its very small. You'll need 73-76 A body upper control arms and 73-76 lower balljoints to go with the spindles, etc. from the F, M,J or late B. Its a very nice inexpensive single piston caliper set-up.
I know of dozens of people who have used this swap (including myself) on their A bodies and a couple on early B's with no problems or adverse effects. I have also sold a bunch of these set-ups without a single issue.