Spent a good few hours this week tuning the qjet on my 66 Starfire. I couldn't get it to idle correctly.

Turns out the original brake booster has a vacuum leak big enough to throw idle mixture way lean

I converted this Starfire to front discs using 1970 factory rotors & disc brake dual m/c. But the master cylinder is bolted to the original factory (8"?) booster. Which is now leaking. No complaints after 50+ years service.

It looks like going to 9" (per 1970 factory spec) or maybe even 11" would be a good upgrade. It's a big car, so there might be a little more room between the engine and booster than the Cutlass/442.

Does anyone know if an 11" brake booster will fit 65-70 big cars?

With the 66 booster and 70 m/c, the brake pedal feel has always been vague since the disc conversion.

Thanks for any guidance you can offer.
cf