I wish I saved the link, but not over 2-3 weeks ago there was a 40s Brockway tandem highway tractor with a Diamond Reo 450 ohv inline SIX on ebay. 450 cubic inches, can you imagine. Of course, I guess parts are unheard of. I think all the big truck makers had big gas 6-cylinders back then...Mack, Reo, IH, GMC.... :p Probably the 292 or 302 are the only realistic choices for a big gas six in your AD pickup. Good luck!
