4 bolt disc brake m/c

Well it has to be 77 and earlier. 78 up has the plastic tank aluminium body. I would guess for power brakes. Is there a groove for the rubber retaking ring for manual brake pushrod? What is the bore size. I would think it would work on A, B,C,E,F bodies and trucks. As long as the bore size is what the ppl are looking for. Kim. Don’t forget that master cylinders were changed randomly years back if the customer or do it youselfer couldn’t get the right part for the application. And even then stuff was grouped together to fit multiple vehicals. Kim