I use 3/4" heims.... When I want to go really fast, I use moly tubing with threaded bung inserts welded in to the 1 1/8" .083 wall moly.... For just fast, I use 1", .156 wall DOM tubing then tap with a 3/4" LH on one end and a 3/4" RH tap on the tubing....much easier to make bar length adjustments with a right and left heim on the ends of each tube.... Use some high quality jam nuts on the heims, too......