[HWYSTR455]

I've had very good results with Pirate Jack over the years, boosters these days are a high fail-rate item.

https://piratejack.net/1964-1972-gm-...its/disc-drum/

Pretty sure OE for a Disc/Drum setup is 1 1/16 bore, but you can adjust for desired pedal feel.

If you're replacing both, you can consider going to a smaller booster, if you're not concerned with originallity. A 9" dual diaphram is a nice upgrade, gives room for tall valve covers, and a little extra boost, especially in lower vacuum situations.

If you run headers, and you did a make-shift relocation of the combo valve, order with a new valve and bracket, and the front line conversion kit. That will clean it up very nicely. You get a union, and a short length for the rear line, so you don't have to replace the whole rear line.

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