ok on a 2 ton car a 1 lb fuel pump isn't gonna change anything
(btw mechanical pump is prolly half the weight of electric)
its a old v8, have way more power than they know what to do with, i bet the hp needed to bump that fuel pump (turns 1/2 the speed of the engine rpm since their commonly driven off the camshaft, meaning it gets bumped once every 2 revolutions of the crankshaft) is 1/32 of a hp...you will
not see any mpg gain from switching. You can save 10X as much fuel by going 1 mph less than what you normally go lol...
and joe bob i have to ask why you change your waterpump every year?