The Hyd Roller cams use higher spring pressures than flat tappet, so that is one thing that has to be upgraded. We offer what we call “K” kits. These kits make it easy to get all the parts you need for an easy conversion.
Also the additional height of the tie bars on the lifters can hit the bottom side boss on the valley pan. This has to be provisioned or you can buy a version we have made that clears.
Bronze or polymer distributor gear (Butler Recommended) is needed on Billet cams. Some manufacture’s say the melonized gears work but we haven’t tested this on our engines and would lean to the side of protecting the investment of the cam with a gear made from softer material than the cam.
To run 1.65 you may have to slot the pushrod tubes. The 1.65 rockers have a seat cup that is positioned closer to the rocker stud which changes the angle of the pushrod going through the head. In some cases this could touch the wall of the head. Usually elongating the hole from the top about middle ways down the tube is all that is needed.