Seems I miss spoke here. The input shaft is the same diameter and spline count, but GM used a tapered 10 spline while the gear box are straight spline. The output shaft is 1 1/2" 10 spline.

But I do have some good news for those ho have been following this thread.

The Aux Gear Box is. . . hold you breath now.

Is a Watson from H.S. Watson Co. of San Francisco CA., but it was manufactures by...TA DA drum roll please Brown-Lipe of Toledo Ohio for H.S. Watson.

New pix have been added to my collection.

http://s1253.photobucket.com/user/GMCPic/media/Gear%20Box/WatsonGMCrecommend.jpg.html?sort=3&o=0

All hail Klaatu and Gort

Dance like no one is watching,
Sing like no one is listening,
Love like you've never been hurt.

1948 GMC FC101 1/2t Pickup w/270 and SM420
1948 GMC FC253 1t Factory 80"x9' Flatbed Dually
1948 Chevy COE 2 Ton 8'x15' Flatbed
1950 GMC 354-24 2 Ton 8'X12' Flatbed w/Dump Hoist
1953 GMC 454-30 3 Ton 8'x14' Flatbed w/Dump Hoist
1953 GMC 454-30 3 Ton Cab and Chassis
1942 Clarkator 6 MILL-44 Heavy Aircraft Tug
1942 Ford (9N) Moto Tug with 1/2 yard Loader
1947 Oliver OC3 HG-42 Tract-Crawler Bull Dozier w/6' Blade