Brakes

Fellows I am haveing a heck of a time getting the brakes to work
properly on my 51 Chev I sure could use some help.
I started off putting 1978 Buick Skylark disc brakes on the front and
72 chevy nova drums on the back, Installed a 1978 Camero master
cylinder and Booster pot. after plumping the brakes and bleeding the
master cylinder, brakes and porportioning valve I seemed to have good
brake pedal, that is until I started the engine, then the pedal went to
the floor. I since then have redone just about everything that can be
done to the brakes with the same effect.
New Master cylinder (bigger) new Booster Pot, new calipers (Cadillac)
new porporting valve new lines, check valve on back line, etc etc.
I have a Camero Maintainenc book and in there it tells me that there is
an adjustment on the small pin that sits inside the booter and into
the master cylinder there is supposeably a guage called a go-no-go
gauge with which you set this small pin outside of the booster. I have
talked with a fellow hot rodder in Hawaii who has the same car as I do
and he was telling me that the pin has to be just right or the pedal
will go to the floor when the engine is started I have tried to adjust
this but I just can't seem to get it right
CAN ANYBODY THINK OF ANYTHING ELSE
Chantz