.557" purple shaft 318?

I am wondering if any one has run a .557" purple shaft in a hot 318 set up?
Will it have enough vacuum for power brakes? I'm thinking of installing a booster tank under the guard to help.

I want to try the .557" in my std bore 318 that has .040"off deck and the four valve relief pistons which are .020" taller.
Out of the box Eddy heads with bushed Speed Pro (273) rockers.
Holley Strip Dominator intake with modded 600 AFB (secondary initial discharge ports enabled and dual fuel inlet -6)
Accel billet dissy with Mallory coil
Extractors tri-y with large port header flange, twin 2 1/2" short exhaust.
4000 stall full manual 904 and 4.11 gears in light weight Aussie A Body




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