Ok so I should go with the solid roller before the flat tappet. Im still on the planning on the build im trying to find what would work ad what I can do with.
is this a magnum block? if so, a hydraulic roller cam would be the best bet since the hydraulic roller lifters for it are only around 140 bucks and the cam maybe 300, where a solid roller cam at the same price would add probably another 300-400 bucks for the lifters.
You also want to think about what size you want this motor to be.
You could build it as a 318, or you could put a 4 inch stroke crank in it and build a 390 which could be really badass.
The cam choice between the two would be two different animals though, so I think you need to really think over what size motor you want to build first, what cylinder heads you want to use, and then the cam could be picked to go along with it last.
picking the correct cam specs for your engine can make or break the engine. Too small and it will never live to it's potential, and too big can make it a complete dog.
Back to the block though, first things first, you'll want to determine what block you have. if it's a magnum block, on the rear passenger side, there will be a pas where a crank sensor goes, in the valley where the lifters go, there will be holes for a retainer plate...if you take a picture of the block we can spot that stuff right away and put together a "grocery list".