Went to order a new fuel pump for my 1986 170 from the link above and serial # doesnt match up for a 170 so which pump do I need ? It shows 170 serial #s starting @ 69 and up but my motor has 170 on the valve cover along with the serial # of A634451 which if I looked @ the list right this # would fall in the 470 era, Right ? No number to be found on pump.