You are correct about the 848 head on a 261. Which from what I have read here on the site is not a problem if the steam hole in the water jackets were slightly open up. Does not have any issues with overheating. I didn't build the engine, wish I did.
Jeff 1964 Chevrolet K10 Fleetside "A Kid's First Truck" Follow in the DITY 1951 Chevrolet 3100 Follow his build in the Project Journals 1969 Chevrolet Camaro Convertible | 2020 Chevrolet Silverado | 3500 Duramax | 2021 GMC Sierra Denali USAF Veteran 1983-1987 | PSP retired 1990- 2012