Get the shift pattern, if the ball is there. NP have Al top covers with 4 shift rails, Clark Al top covers in some, have an 'o' in their MN as above, most all have an 'o' in the MN. Retainer dia might be larger than 3 or 4 speed, bore bellhousing out. There are short(like most 3 speeds) and long input shafts, 10" or so, for 14" clutch, so if one gets long one, better get the whole assembly.

There is a factory GM adapter that puts a small block on a 14" clutch assembly, consists of 1/4" plate to register and bellhousing, I have one if you need px.

One of the problems is OD is gotten by taking 3rd. gear position, so, if one has a load, no two speed axle, then you are stuck in 2nd 'til top of hill.

Ed

Last edited by EdPruss; 11/29/2016 6:25 PM.
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.