At what vacuum level will you need a vacuum canister for good power brake operation? At what point will a vacuum canister not be enough and a electric vacuum pump be needed? Is their some general rule of thumb on this?
When I had my last engine which was on its way out (burnt valves, worn guides, rust marks on the cyl walls) I was pulling 5-9in of vacuum in gear. This was just enough to use power brakes kind of. Adding a vacuum can didnt help as I only rarely hit 14+in of vacuum when snapping the throttle shut. Using a pump made it dramatically better in terms of pedal feel.
I don't know what level of vaccum, but in terms of cam choice, I was running my power brakes in my Ranger fine with a Z303 roller in my 331. (.587 lift/228 degree duration @.050)