To accurately set lifter preload you really need to start with a adjustable pushrod, I made several from old p-rods. Get the zero preload P-rod length, then add a minimum of .025 or .05 to the base line. Like Zaedster wrote, reducing the cam lobe base circle will reduce lifter preload. Rebuilding the heads requires regrinding the valve seats and valves, that increases lifter preload by a factor of the rocker arm ratio(1.8-1.65-1. The increase in installed valve stem height after the rebuild X the rocker arm ratio will give the increase in lifter preload. Same as decking the block and resurfacing the cylinder heads increases lifter preload 1-1. What I am getting at is that unless you plan to go wild with the cam and making some major changes in the engine geometry, you will be ok and avoid a preload issue. If you have any ticking after running the engine in, than verify the loose lifter and increase the p-rod length.
