That's what I have always ran is flat tappet, but that 318 Magnum was my 1st hydraulic roller cam and then this 1987 318 LA would be my 2nd hydraulic roller cam engine.
i think that i may have missed the mark trying to adequately articulate my thought: if you don't already have a roller cam, it's stupid to get a factory .390 unit when you could have something so much better for basically the same monies.
if you already have a roller cam, then just get it regroud to a spec that will compliment what ever it is you decide to build compression wise.