Another vote for the Briggs Vanguards!! :thumbup:
I have a lightly modded 23HP Vanny in an EZGO golf cart.. It has a performance cam, rev-kit, and header.. It puts out nearly 30HP and can be buzzed to nearly 6000 RPM... The cart has a set of 8:1 hi-speed gears and will nearly hit 40MPH at WOT...
I feed it to my old diesel pickup.. That 'ol 7.3 loves used oil & ATF, it also keeps the cost of feeding it reasonable with diesel nearing $4.00 a gallon..