I'd go with the GM. overhead valve, inline 6. parts are relatively cheap and available. That's not to say that you couldn't put an ohv engine in an early ford. I daily drove my 59 chevy truck for almost 2 years (261 cu.in. inline 6 and an np540 5 speed) and could do 60 mph easy and it never failed to start a single time. The only thing I did to it was adjust brakes and change the oil. pretty painless.