Start by looking for a 1955 or newer, that's for both 235 and 261, the 1954 and older have doweled rod and main bearings that are really hard to find. My 1959 261 was bored 60 over and I had a hard time finding pistons. Once I found pistons I couldn't find rings for them because of the wide ring groove, I had to go right to Hastings and have them made (not cheap). All the rest of the parts for the overhaul were easy to find, but you have to shop to find the best price. This was about 4 years ago so it probably hasn't got any better.
P.S.
Then there's finding a machine shop that isn't booked out for the next year or so.

51 GMC 100 with 59 chevy 261 under the hood.
3 on the floor with 3.42 gear.