Another question about my P&W square head C

I have the newer P&W model C, the head stock is square and has the up-grades. One being the back lash adjustment on the cross feed screw nut. Simply put is a jam nut that has worm gear OD. Adjustment is made by turning 2 socket head cap screws, loosen one tighten the other rotates the nut. But on mine the screws can't be tightened, they will push away from the worm. The worm gear is in good shape. To help I made a cradle for the lower ends of the screws to keep the screws from separating better but not much. Not being able to tighten the screws the adjustment will change and back lash will increase. If my memory is correct the new to me lathe came with 3/8-16 cap screws, I replaces them with new but that didn't help. 16TPI fits the worm gear but 14 will also. However 7/16 don't fit in the hole. I can't remember what lathe I had, wasn't P&W but it had the same type adjustment however the screws were able to be tightened. Anyone know what the screws should be? I do have both owners and parts manual but only part number is given.