I'm faced with this problem right now also. I have a 85 351 and would like to have a roller cam, but I'm not going to go with the 302 retaining hardware due to having to take the bottom end apart for drilling and tapping holes, and machining the block where the dogbones can lay flat, I was also informed that I would need a small base circle cam.
I also don't want to pay a gazillion dollars for link bar roller lifters.
That leaves me no other choice than to stick with a flat tappet. People have been using them for years.