Isnt the volvo master just a 3/4 master? Figure out what size the bore is and replace with one thats the same size bore that fits the hydroboost, done and done
I am not really sure exactly what you are saying, so correct me if I take this in the wrong direction.
The GM master cylinder that comes on the hydroboost has driver side outlets for the brake lines, this makes getting lines to it troublesome. It is also very tall, although I don't think that would be a deal braker.
The next issue I had with using the GM hydroboost (HB), was that the studs to mount the master cylinder (MC) are a couple mm farther apart than the Volvo unit. Again not a big deal, I just used a round file and opened up (slotted) the Volvo MC holes enough to fit.
Step two was creating an adapter - this is really only a small sleeve that fit inside the HB unit to decrease the mount hole down to the size of the Volvo MC cylinder. The center hole in the HB unit is about 10mm larger in diameter than the corresbonding area on the Volvo MC.
Step three requires extending the the HB push rod (the one that is in contact with the MC) because the Volvo MC also does not fit as deeply into the HB unit as the GM OEM MC does.
Fianally, the push rod that attatches to the Brake pedal is to long, requiring cutting, shortining and welding the rod to fit.
None of these precludes the use of this HB unit, all can be overcomed, but after researching (which I should have done first) I found that the Mustang HB and MC units fit much better, are a little smaller and are cheaper (at least in my area).
With the Mustang units, there are 1", 1-1/16" and 1-5/8" bore master cylinders available. So, rather that being limited to the Volvo MC bore size (I am unsure what that actually is) and the amount of fluid that can push, you can attempt to tune the MC to the caliper bore sizes being used. I think for most people the 1" bore will get the job done, but if someone went crazy on caliper size, there would be a few other options.
Personally I am using the 1-1/16" bore MC, I am also running very large Brembo 4 piston front calipers and my rear calipers are the same ones used when upgrading to Brembos on the front of newer Mustangs. This is almost certainly overkill on any street (very occasional race) Volvo, but I got a good deal on the calipers and I was able to make my own adapters to get them to fit.
Again if I got away from where you were going with your post straighten me out.
Thanks, Jeff