yes; the bores vary from 7/8 to about 33/32 .. Each bigger size offers less foot travel, but has the potential to transmit more hydraulic pressure to the calipers, but will require more leg force. Since disc brakes are NOT self energizing, all other things being equal, it requires more leg power to make the same-as-drum-brake stops. This is why you see boosters on almost all Mopar db cars. Because the booster is so powerful, it is able to operate the big-bore MCs with very little leg-power. Now, if you transplant that big-bore MC, leaving the booster behind, then you end up with your situation. So; you have a choice; re-install the booster, or get a MC with a smaller bore. With the latter, there are a couple of things you have to work out. 1) Because the the new bore size is smaller, there is less volume of fluid in the chamber. So, it takes more foot stroke to push the fluid out; You better not run outta room to the floorboards, with a max-effort stop. But more importantly, if the rear system fails by catastrophic leak, your pedal will drop another inch to inch point five, during the brake application. Again, you better not run outta room. 2) because the MC bore is smaller, there is less fluid in the chamber. If your particular calipers retract too far from the discs in normal application, it becomes possible for all the fluid in the chamber to not be enough to push the pistons out AND still have full braking power. 3) this is why, for you, I recommended to find a booster, because your system is already designed for it. Just swap it in, set the pushrod length, remount the MC and yur done. 4) because db systems are NOT self energizing, this can be a problem for a non-boosted car, when stopped on a hill with the front of the car higher; the car will want to roll backwards. So you may have to apply more pressure. During a long traffic light, it might happen that you lose concentration, and the car rolls back into the vehicle behind you, and guess who's at fault. Same goes for if, for whatever reason, your car is on a fast-idle, in gear. A large-bore MC,without a booster, just makes all of this just so much worse. So, when the question comes up; does your lightweight-A need a booster? Most of us might say no it doesn't. Your braking system can be engineered to operate satisfactorily, for a high percentile of persons, for a high percentage of the time. But I submit, that it's nice to have.
and can I tell what I have. only by pulling it off the firewall and measuring it.
2nd what booster would work? any with same mounting pattern
and what (if any) modifications would be needed to add one? adjust the pushrod length
