i never heard of the oil pump or dist gear to make such noise but that's just me, not sure if possible
i doubt it's the pins but then again nothing's for sure. if it really bothers you you'll still have to take it apart to fix it even if you figure it out before doing so.
start by measuring the preload, that can tell you the state of the cam and/or valves since you replaced everything else and take it from there. You can also bring the pistons in compression and rotate the pushrods, it can tell you if some or one is rotating freely then it means there's no preload. You can also spin the oil pump by taking out the dist, i doubt that's your issue, the noise would be different though it's hard to confuse it with piston slap or lifter noise.