[F.A.A.benny]

I vote for restoring an original system. If staying with r12, flush, pressure check both the evaporator and condenser. Test the poa valve to make sure It isn't stuck. Check the screen in the exp valve. You can clean it with some brake cleaner. Replace the drier. They are cheap. Some reuse their hoses/lines if they are in good shape. Hoses should not have cracks. Buy an aluminum a6 replacement compressor. Use mineral oil. If going with 134a, replace original condenser with parallel flow condenser. Recalibrate poa valve. Some will say to replace expansion valve but an original will work fine with 134a. I'd replace the hoses. Use pag oil. All this can be done for less than an aftermarket system plus it all bolts in and you get to keep the fresh air option.