early a master cylinder swap

Not sure what a fruit jar is but here are the brake mods I have done my my two cars.

1965 Signet. Installed 76 Dodge Dart M/C with front disks (sliders) spindles lower control arms and the bigger upper A arms rear 10 inch shoes with the proportioning valve. 15 inch rims no grinding on calipers.

1964 Barracuda. Installed 76 Dodge Dart front disks (sliders) spindles, lower ball joint, put a bushing in on the upper ball joint. KEPT the original master cylinder (maybe this is what you call a fruit jar? perfectly safe) Did not use proportioning valve as I kept the rear 9 inch brakes. 14 inch 5 1/2 rims spacers and grinding required on calipers. This car is all stock that is why I kept the 14inch rims.

Both work great ask if you have any questions. If I were you though I would look at putting on disk brakes.

I used the RAM MAN set up.