Have poured a lot of time and money into a replacement dual res power brake and booster bought from ID in NM.System is sound,vac right up there.Brakes will not work.Going back to original Bendix Treadle Vac system but inspection shows inside of booster corroded and should be replaced.It is 6"diameter.Was wondering if later 5 1/4" unit would be a bolt-in replacement ?Would like to hear from anyone who has done this switch and any good source of parts(larger unit scarce around here).Thanks