How fast do you want to pull that trailer? What hills do you want to climb.
If you are content running slower than most the traffic the 235 or 261 should be fine. For more power you could also look at a GMC 270 or 302, or maybe even a more modern Chevy 292.
I can't imagine being happy with a 235 pulling a trailer, but I like to run a little faster, at least with traffic.
A few years ago I caravaned with several others including a '57 Chevy wagon with a 235. Going across Idaho and Wyoming were speed limits are 70 and 75, the '57 Chevy limited our speed. It fell behind on the inclines and was not comfortable running that fast on the flat areas.
To put that in perspective, I was driving a 350 powered pickup and pulling another '57 Chevy on a dolly behind me. I was easily able to run the speed limit even uphill. The 235 powered wagon couldn't keep up.
Don't get me wrong, I'd love to own that wagon, but I'd never choose it to pull a trailer at highway speeds.
