A built 235 will handle up to 5k trailer with a 5 speed. You are pulling 11K at speed go V8. A 350 would pull your load just fine!
Run a gear ratio between 3:50 and 4:11 for your gcvw. Prefer gear splits of a 5 speed trans but autos work well also.
47 Fleetmaster, Hotrod 6, 5 Speed
50 Sedan Delivery, 327, 5 Speed
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