Whats the right size?
 

Recently I decided to remove the stock heads on my 90 GT. For more HP I went with World Products Dart Winsor Jr heads. I also upgraded the rocker arms, and went with crane cames adjustable roller tip rockers. What I'm not sure of is the proper length of the pushrods. Should I use the stock ones or should they be longer.

Depends really, check the geometry of the valve and rocker as it rolls through its motion. For the most part if the rocker tip stays toward the middle of the valve stem then its not to bad. If the tip washes over either end of the valve stem then the geometry's off.