I was going to try to stuff 3/8 dia. pushrods but I would have had to copper tubes sleeve the holes in the head as when I tried to clearance them a little bit, I was starting to break thru the port. I ended up going with 5/16 x .083 wall. Can't remember the exact lengths. I can tell you lengths when I get home from work.

Stock 5/16 pushrods are .06"-.065" wall if I remember correctly.