View attachment 1715973717
This is the aluminum Rallye from Year One. They are 17”. The 15’s are steel.
I think you should make a priorities check. What are your main concerns? Convert to disc? Check. 15” vs 14”? Bigger tire selection in 15”. Check.
Is the bolt pattern size important to you?
Sounds to me like a swap to the 1973+ disc spindles and larger single piston caliper is your best route. It gets you the 5x4.5” stud spacing. Just buy the bigger bolt pattern axles for the rearend at the same time.