I think the difference between the 235 and 261 would be very noticeable. I replaced my 235 with a 261 and the difference was night and day. The 261 came out of a 1960 Viking series 60 school bus. That bus had no problems even loaded rolling down the road at the speed limit at the time. And would pull hills like crazy. I put it in my little 58 half ton pkup and could haul anything I wanted and had plenty of power.
