Just throwing this out there too, you can get the disc brake kits for the older 620s... I have a set of the 300zx on my 77 from Beebani, and I love them.
I love the fact that I can open my hood and point to anything and have a pretty good idea what it is and what it does, not to mention fit my hands in there to fix something (When the wife asks me to look at her honda fit even for a simple oil change, I cry just a little). Not to mention that when something does go wrong, its easy to diagnose and you dont have a million and one sensors that cause more problems than I think they are worth. I got my truck from Cali and I must say the frame was near mint! where as out here in New England things dont last too long with the salt and snow.