Slip yoke question

Came across another issues (fun stuff) on my 727 swap. The trans is bolted in ready to go and I went to install the slip yoke that I purchased to get a final measurement on the driveshaft. Well the slip yoke will only go into the tail shaft of the trans about 3/4" and it hangs up. This yoke is supposedly for a 727 with the large U-joint my question is are there more than one slip yoke for the 727? Were there yokes with different number of splines? The yoke and its splines are in good shape it just won't slide all the way on. I am glad I love this car b/c it sure can be frustrating!