Join Date: Jan 2015
Location: Injun Territory, 'Merica!
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have yet to run across a 2" diameter stock GM driveshaft of that era, sounds mighty weak. A stock '73 GTO with turbo 400 or Muncie 4spd is going to have a 1piece driveshaft (none of the rubber isolated 2 piece nonsense) & the diameter of that "73" driveshaft is going to be 3". IF, after several inches from the ends, the driveshaft steps up in diameter a few inches, that center area, will be near 3 3/4" in diameter. Thinking back, dont believe the '73 style driveshafts have the step up design. Its been years, but I used to pull straight '73-75 2door LeMans/GP/GTO turbo 400 length driveshafts for next to nothing, & have them cut down to make correct length turbo 400 driveshafts for late 2nd Gen Birds. FWIW, the original '73 GTO/GP driveshaft will have 3R ujoints, '73 & 74 Chevy A-bodys will have the smaller spicer 1310 ujoints.
Quickly looking at oem GM driveshafts, the smallest diameter stock driveshaft in my driveshaft barrels is one from a '78-87 ElCamino. I kept it in order to note the stock length. Pulled it out of one of the first ElCo's I built an 8.5 G-body rear for, & then went with a 3" diameter driveshaft that was 7/8" shorter. no way I'd install that flimsy thing behind a Pontiac building any kind or torque.