George,
3836850 is a code for a 261 head over many years. What is the head date casting code (under the valve cover - check the link I gave in my earlier post).
That head could have been put on your 235 at some time over the years.
Are there screw holes on the top of the head, outside the edge of the valve cover (2 holes on each side of the valve cover, for the original valve cover)?
