Usually the stamped number behind the dizzy can help identify the engine, but thats not always the case with the later 235's. The date code is cast into the block near the starter. The casting number for the block is below and forward of the dizzy.
As far as I know, all 56-62 235's had the 848 head. 913 is an earlier head with very slightly less compression. Date codes for the heads are on the pass. side center.
Likely, its a late 235 that needed a new head, so they just grabbed what they could find. What size is the temp sending unit hole?
I don't know exactly what the comp. ratio would be on a 261 with 848 head, But I have CC'd a head and was in the process of finding out when I got sidetracked. The 848 head I checked was made in 1962 and had about an 82cc chamber volume. I believe the head gasket had a .055" compressed thickness, but I'd have to recheck that. The rest you can figure out for yourself.
