Roller Cammed 318/360
Heads up on your machining issue - some blocks do not allow it. Attached is a picture of a resto 340 block (similar to R3) that was ruined by such an attempt!
(the threaded hole between the lifter bores was for ceramic lifters .... another story!)
Other point is Mopar's large diameter lifters - you can run fairly aggressive ramps without needing a roller.
Kory