Does anybody know the difference between the ac delco Fls1015 and fls1034 sending units. Rock auto lists the 1015 as standard for my truck (95 k2500 5.7l) but the 1034 for a 95 7.4l and 96-98 5.7l, same fuel tank listed for all. Want to get a ep377 pump and a new sending unit just wondering what the difference is because the 1034 is like half as much as the 1015.