261's are a neat engine, externally they look the same as a 235, except for the "Captains Bars" cast on the side of the block near the starter. My 59's original 235 had a cracked block from one end to the other the first time I rebuilt my truck, so I swapped in a running 261. Drove it for a few years with that engine with stock suspension and drivetrain. The engine ran great but the stock tranny and rear end meant I couldn't do much more than 50 mph. I was thinking about just keeping the 261 for a while and putting an overdrive behind it, but finally decided to switch to a 327 and 700r4 when I did the camaro clip.