Started the conversion to 11" disc on my 66 442. My question is Can I keep my 9" booster and just replace the master and combo valve. I already purchased the spindle kit , and will buy new rotors and calipers Saturday. The combo valve is easy choice , What master would be used year or pt # would help. and would I have a travel problem with the existing booster / pin. Also I can't update to a 11" booster (455) no room. Done befor I purchased car. I know all this stuff has talked to death but I could use the info.

 

The stock booster on a 67 442 is the 11" booster (same P/N as on the 68-72 cars), so I don't know why you think it won't fit. Get any A-body disk brake M/C. Your choice if you want the dual bale style or the single bale style. If your 9" booster has the correct pushrod for a dual circuit M/C (with the shallow hole in the M/C for the pushrod) then the disk M/C will bolt right up, but boost will be limited, especially if your engine has low vacuum.