Actually presently the fuel pump is mounted in the fuel filler plate and driven by a long cable off of the back of the oil pump (i.e.dry sump) some off the back of the camshaft,and some off the bell housing/flywheel, not off the differential. I would think Nascar would mandate a mechanical pump although reading that Waterman link about the electrical fuel pump it says they have several safety systems built in,but it didn't really give any details. Either way I don't think Nascar takes any thing safety, lightly. Waterman also makes some of the cable driven pumps currently used.