I've heard late model S-10's and Astro Vans have masters that are direct boltins. Sorry I don't know what years I think I read it here on Team Chevelle. Maybe try a search on it? Well at least you know what models to keep an eye out for I know those were the donor vehichles but the years have slipped my mind!
Anyone want to jump in with the years?
Not sure if the aluminum master cylinder is a bolt-on but it can be done. On my 66 A-body, I have a dual-diaphragm power booster from an 85 Cutlass with a 87 or 89 master cylinder from a Impala. Adapt the booster by grinding the rivets off the A-body power booster brackets and remove them. The late model booster has a slightly different bolt pattern and metric studs. Slot the bracket holes and they will bolt on. You will have to adapt the plunger rod on the booster to mount to the A-body brake pedal. I cut it short, threaded it 3/8-24, and used a coupler and all thread.
The Impala master cylinder has the same bore size as your Chevelle. The dual diaphragm booster is great for low manifold vacuum cars like my 427 power car. I'm lucky if I get 10 inches vacuum at idle (the solid lifter "bump stick"). Since I installed this engine just over a year ago, I have run out of power assist only once.
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