Interesting feedback. Thanks!

Yeah, I guess you could build a gas version of a 4-stroke diesels (and I think all the Macks were). A 500CID flathead? I can beleive they used to make one; I had a buddy with a 1936 Diamond Reo with a big 'ol flathead I-8.

140 HP is plenty! All you need is lots of gears... ;-)

Cheers!
George