i'm in the process of having an engine built for my 49,a .30 over 350.i just had this conversation with my builder.he builds alot of race motors and a pretty busy guy so i would hope he knows what hes talking about.he said pretty much it didnt matter either one would work since their internally balanced.se said they would run fine without a balancer.that their basically a place to bolt your pulleys and to keep it from leaking oil out the timing cover.i asked him which he preferred,and was told the 6 3/4 only because of less rotating mass.but then said its not that big a deal.i had bought a junkyard 8" he said it wasnt worth spending the money to switch either would be fine..........dave
