Your Dad might be right. From your handle I am guessing you live in Ohio. If this is northern Ohio is can get pretty cold in winter. The gas tractors will start easier there on cold days, thus, your livestock has a better chance of getting feed. Here in West Virginia we have a Farmall guy who owns a 656 gas for that exact reason. He rarely uses it, but has it just in case of a bad winter.
As far as bad press on the 1855 diesel, that is because of the original connecting rod bolts, and wrist pin bushings. There was a refit kit to upgrade this, it is likely that if the tractor you find doesn't have a hole in the side of the engine block, it probably has been upgraded. I wouldn't rule out that there are some low hour originals still out there, but it would be a rare find. If the engine has been rebuilt at one time or another, you shouldn't have this problem. As it was an early problem, and it was detected early on, then corrected.
I hope this helps.
Andy