Hi Puffie40, welcome to the site. I can't help with the 6 cylinder questions, my big bolt is a stock 283 V8. The 2 speed shift valve is pretty simple, it looks like the crack is not in the vacuum portion, you should be able to reinforce the housing with some light metal. The HrydoVac system worked well for thousands of trucks, I rebuilt all of the wheel cylinders, master cylinder, and HrydoVac, brakes work like a charm.
