Finally got to drive it.
I chose to do this swap because I had the parts, and my stock differential was shot, and I broke a stub shaft.
The infiniti brake calipers are far superior to the 79zx calipers, the infiniti rotors are dimensionally identical, but use a drum style emergency brake.
The infiniti differential is 3.9-1, the stock is 3.7-1.
It widened the rear hub to hub by about 2”.
I plan on building another zx, but I plan on using the j30 underpinnings.
I doubt this is a swap that would be worth it to anyone who didn’t have the parts on hand and easily accessible.