Looking down my lifter bores the cam lobes don't seem to line up in the center of the bores. They are offset towards the back of the block, but are still completely inside the bore diameter. Do I have a problem? Thanks - new engine builder.

That's the way it should be on a flat tappet cam. The lifters aren't centered on the lobes, but shifted toward the front of the lobes. The lobes are also tapered slightly with the high side to the rear. All this, with the slightly convex face on the lifters, is to help the lifters to spin and also to put rearward pressure on the cam (via valve spring pressure), so it will not "walk" forward. The rear "stop" is the timing gear against the block, separated by a cushion of oil.