If you drill out the restrictor fitting a bit and use a pinched off rocker connector the 1959-62 rockers will also work fine.
As far as 235 verses 261 rockers, I would not worry about that. The difference is the vent hole location. It may be in a slight different position, as the 261 truck rocker looks like Chev wanted to direct a little more oil over to the valve. For low to medium work load that will make no difference.
