Maybe I was too obtuse above and too tongue-in-cheek in the earlier post of the "Rare Chevy flat headsix". Also, sorry I forget to include the link to the earlier discussion (I edited my post above and the link is now there - the original eBay listing is no longer available this morning).
Chevy did not have a flathead six (of course, Ralphy is correct). However, texacowego might have a non-Chevy flathead engine in his truck, placed in there by someone who did not have access to a 350 V8.
Ralphy, Do you have the eBay name of the person who listed that truck with two different engines (and two different engine bays)? People might want to avoid bidding on his listings, even though they might be good for a laugh.
Tim