The 302 option looks promising. I have a graveyard of M-135 series trucks and I hope there's at least one good engine among them. On the other hand, I could waste a lot of time trying engines out. I also have several 235's, mostly from '55 Chevys, if any parts off them are useful.
Since my 302's are all military, there are a few more questions that come up:
They are 24 volt. Generator is no problem, since I plan on a 12-volt alternator anyway. Starter will be a problem. Will the 12-volt starter off a 235 work, or will the 302 starter have to be rewound for 12 volts? I can use mechanical gauges, so no voltage problems there.
The military engines are all automatics. Will the 270 flywheel bolt on in place of the flex-plate, or did they do something nasty, like use a different crankshaft flange?
The military engines have sealed ignition systems. Good for an engine that has to operate in a wet environment, but a mixed blessing. For one thing, replacement parts cost several times as much as parts for a conventional system. For another, having all the connections inaccessible makes troubleshooting a lot harder. What conventional distributor will fit if I give up on the sealed system?
The DUKW has unique clearance problems caused by the front driveshaft and axle tubes. This results in an oddly shaped oil pan. Will the 270 oil pan bolt onto the 302, or will I have to cut and weld the 302 oil pan until it looks like the 270 pan? This is something I'd probably have to do the oil pans of any of the other alternatives, so it's not an argument against the 302.
