Will a 90 steering shaft fit in a 71 box?

[71K5]

need to change my steering shaft in my box out so I can get the smaller splines on the input. Changing my rag joint out for a van u joint. but the 71 shaft has too large of splines for the u joint to fit.

But it does fit on a 90 model or in theory an 80's

so I want to get a box from the yard with the shaft I need and rebuild the box with the new shaft if it will all fit.