A couple pictures of a '66 Mustang

Irrigation systems had pumps powered commonly by the Ford Industrial 300 cid Six. Those engines would run full throttle for a couple months, get shut down for service then fired up and ran at full throttle for another couple months. The only engines that I know of that could run like that and take that abuse was a flathead Chrysler Industrial or the F-series Continentals. They were extremely tough engines.

There was a flathead 6 earlier, then a "big" series of Ford OHV 6's and a "little" series of Ford OHV 6's. Perhaps MR MEZ would be good enough to fill us in more completely.

WC

My '66...
It has the 200 6, C-4 dual range auto transmission.  It does have some frame rust that is concerning me now, but in talking with a few shops around town I believe it can be safely repaired.  Time and money will be an issue  

Not real important to the discussion, but I have seen the Ford 300 6 Cylinder used for Emergency Generator service, operating on Natural Gas.  

Nice looking car! Fixing it up would be money well spent.

They may reproduce the parts you need. Good luck.

WC

Very nice car, I'm sure the frame can be repaired. welding/fishplate