Technical Pushrod question

Could someone school me on fuel pump push rods? I have an 8BA engine with a Thickston PM7 intake manifold. I want to run an early mechanical fuel pump. Do I shorten the larger diameter pushrod to the length of the earlier rod intended for aluminum intakes? Do I shorten the end opposite that where the grooves are near the end? Are the grooves in line with the oil galley? Thanks in advance Glynn.