727 slip yoke

I've got a driveshaft from my old race car tow rig (440 powerred 1979 1/2 ton pickup). I'm not sure if it takes the 7260, or the 7290 u joint. We got 12" of fresh snow in the last 12 hours, so I'll try to shovel out the garage, and check. I think the difference is 2 1/8 for the small one, and 2 5/8 for the large one you need?
Mike