48 Degree R3 Block Using 59 Degree Heads?

You can use a 48 degree head on 59 degree block, but not a 59 deree head on a 48 degree block. All R3 blocks are not siamese bore. You can get an R3 block 48 0r 59 degree with or without siamese bore.
My 340 resto block is is a 59 degree non siamese R3 block with the extra head bolts milled off. If you decide to go with the 340 resto, comp cams is the only one I know offering an roller lifter fits in this block and I have not heard good reviews of them.