Bill, yes it could, but I believe both the 235 and 261 both used flat top pistons throughout their runs. I used the formula I posed above to figure out the new compression ratio of my 216 with the 235 crank. Of course, I didn't change the head. Changing from a flat piston to dished in the same engine would lower the compression ratio, and going from flat to domed (assuming no interference with the head) would raise the compression ratio. I hadn't checked every year, but just did and the compression ratio on the 261 bumped up to 8.0:1 in 1958 and later, so there were two changes in CR over the years, first in 56, and then again in 58.
The 1961 Vehicle info kit showed the 235 having an 8.25:1 compression ratio, and the 261 having an 8.0:1 compression ratio. They share the same stroke, with the only difference being bore and head volume. So swapping any 235 head to a 261 would boost the compression ratio. Not sure exactly how much though without doing some math.
