Big blocks are rather hard on the valve train, especially with the more radical profiles, and the fact that most of today's oil don't have the necessary extreme pressure lubricants for flat tappets, plus the fact that rollers can make SO much more power than flat tappets with similar specs. With that in mind, I'd strongly
consider going roller. When I was building/rebuilding a 427 for my Vega, I talked to every major cam manufacturer, and they were ALL trying to talk me into a smaller roller than the flat tappet I was already running. I finally called Herbert Cams and talked to somebody who was speaking my language ( I think it was Doug Herbert, but I'm not sure, he mentioned his Dad, Chet, in our conversation). Their first suggestion was EXACTLY what I had in my own mind that I was looking for, and the price was GREAT. I installed it with a set of used rollers I picked up at the track pretty cheap, and after a few thousand miles, one of the lifters wiped out. Herbert had me send the cam back to them for repair, cost was like $50 or $75, I don't remember now for sure, but when I got it back, it looked like BRAND NEW, I don't know for sure if they fixed it or just sent me another one, but either way, I was so pleased with them that I ordered a new set of rollers, along with matching springs, retainers and locks. Best money I ever spent on that motor, and I highly
recommend emailing or better yet, giving them a call, and just see how affordable it would be to go roller.