So, I was mistaken if the input is 9.25" long. You can still use it, however, just make an appropriate(about 3") spacer to take up the extra space. Must register the retainer correctly, or, search parts places for a short input shaft w/ the correct # of drive teeth for the cluster gear.
The trouble with making an OD 5th, is they take away 3rd. gear to make OD, thus leaving a large gap if there is no 2 speed rear.

'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.