Will the booster from a 68 chevelle mount properly to the firewall of a 67 chevelle.
I am changing my 67 4 wheel power drum brake car to disc and have a donor 68 disc car. Any help would be greatly appreciated.
Rob

Yes it should i am using one out of a 70 monte, just be sure to use all the components as on the 68.

The earlier chevelles used a smaller diameter booster which was nice and tidy. Think it was about 6-8 inches in diamter.

Later years (about 67 or 68 I think) went to a larger diameter one (about 10 or 12 inches) and GM put the sloped end valve cover on the driver side of big blocks for clearance. My 69 Corvette has this and I am pretty sure camaros used the same valve cover unsure on chevelles. Just watch the clearnace and those nice tall after market covers may or may not work.
the boosters all pretty much swap out, and the master cylinders all share the same mounting too.

Be sure to get the master and proportioning valve from your donor car if possible or several aftermarket houses make the valves available if you are not concerned with originality over functionality.

My 67 had a single resorvoir master cylinder with a block for splitting the front and rear. This is not a proportioning valve and front disks require a dual master cylinder and the proportioning valve. I got a master cylinder from like a 74 camaro at the parts house but it is the same number they used for years and the aftermarket valve so I would not have troubles with 35 year old junk.