FNG here so I hope I put this in the right topic fourm. My project truck is a 47 ½ ton what they call the advance design model. 47-54 type with the round fenders. Mine is the 3 window. Spent most of its life as a farm truck. “Moms truck” is what we referred to it as. I have had it ratholed for a few years. I’m keeping an inline six, 2x1s on an old tattersfields intake. Fenton exhaust, 20 over, mild cam. Street rod look but not the sbc performance. Others have been doing this same build for some time using a Saginaw four speed with two grove input shaft transmission. 1st gear is 3.11, 2nd is 2.20, 3ed is 1.47 4th = 1.00. By using 3.55 rear gears it mates up great with the power band of the 235 motor. I bought what I and the owner thought was a Saginaw two grove four speed that in fact is not a Saginaw but a Muncie two groove M-20 wide ratio from a late 60’s vette. What a good buy a guy would think. And it is but not what I was looking for as this Muncie is a 2.56 1st gear, 2nd is 1.91, 3ed is 1.48, and 4th is 1 to 1. So now I need to figure out which rear end ratio to use. I would like to be able to take off without slipping the clutch and still be able to run along at 60 mph with out twisting the guts out of the motor. I’m thinking the 3.55 would be a little tall. I have six lug disks on the front so I need to stay with six on the rear. Drum brakes would be good. Original rear is a little over 6o inches. What rear end ratio should I be looking for? What do you think I should be looking for that would have that rear ratio as standard equipment? Or is there a different series from GM that would be closer to what I’m looking for. Like the early to mid 60s? Thanks for any help.
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