Thanks for the info. I think I can use the tube as is and put the original firewall clamps on the drivers side of the firewall, then cut the orig 66 shaft and mate the 68 slightly shortened shaft to it via a ragjoint or universal.
Did you find anyone that sells the replacement plastic sleeves that go inside the tube at the lower end?
Thanks, Jamie

 

At the lower end I welded in a bearing since this is being use with a Rod&Custom front end.