mech Roller vs Mech flat tappet cam Q

As far as bushing the lifter bores or restricting the oil, my original set of Isky lifters required bushing the bores because the roller wheel cutout was flat across above the wheel and would open up the oil galley to drain all the oil pressure. I bought a set of Lunati rollers and the cutouts tapered around the wheel which keeps the oil pressure up and look like the comp rollers in the above pics ( at least where the roller wheel is ). I have been running my same roller cam and lifters since 1991 or so and drive it on the street all the time. .570 lift and 270 duration @ .050 lift. Never had any trouble with the setup. I would like to step up to roller rockers one day though. I have been using the Isky 1.6 iron rockers with this setup the entire time too. I'd go with a roller.