slip yoke problem / TF 727

I was reading all the comments trying to resolve an issue with my yoke. I have the 727 and had a company build my driveshaft. They send it with the end yoke and Spicer 1350 joints . After getting it all together and going down the road thought car was going to vibrate apart . I finally realized I have a bunch of vertical end play on trans tail/ yoke. I don't necessarily know where to start . I was looking for a thicker trans yoke but didn't really have a clue this was going to be an issue . It's a TCI trans so I couldn't tell the year for a place start . I see a few have had this same issue. Do I buy yokes till I find one that has less vertical play? Or what is the option ?