Upper Control Arms in Disc Conversion

Hello all,

Getting ready to do the front brake conversion on my 74 Duster and might be really over thinking this hole thing. I got the 74 parts manual and was looking at it to help determine what parts I could get versus different level kits. From my understanding, 73+ all had the large upper ball joint in the control arm and one big thing a brake conversion talks about is changing the upper control arm because the 72- used small ball joints. Is the 73+ upper control arm the same on an A/E body? The 74 parts manual has me confused as it list several different parts numbers for upper control arms as follows: A-body with Drum Brakes (3722 460-1), Disc brakes (3402702-3) and E-body (1857 856-7). Is the A-Body control arms for Drum/Disc interchangeable, why would they have two different P/A's? Also, is the E-body control arm interchangeable with the A-body's? Any info would be great.

v/r
Ron