Beyond the issues with the execution of the selected lifter system in an old Mopar block, how do you make the call for the more expensive, harder to execute roller hardware? I'm still learning so please have some patience. I get the difference between solid and hydraulic tappets and understand (I think) why solid work better at high rpm. So awhy would you go with a roller over a flat tappet? Reduced friction so more HP? Do hydraulic roller do better at higher rpm than hydraulic flat tappet? Seems solid roller would be the ultimate but it doesn't seem like many folks use them on street engines, or at least to the extent that solid flat tappets are used.