When new or after a rebuild you should see no more than 0.010" to 0.015" play. I would start thinking of a rebuild if I saw more than 0.050" play as the hardened part at the end of the yoke is not very thick. After it goes through the hardened part play increases rapidly and if the end mushrooms it will be difficult to remove.
1971 Coupe, LS-5 454, Tremec TKO 5-speed. 490 hp, 554 ft-lbs. Red on Saddle.
Edelbrock Aluminum heads, Roller Cam, Super Comp Headers, Multipoint EFI, 17" Thrust-D's. http://www.corvetteforum.net/c3/zwede