Panel Fan - the '848 head will work fine on the 261, but it will need to be drilled for the 3 pairs of "steam holes" that are in the block and '850 head, to assure proper cooling. Use a 261 head gasket as a template, and note that the holes are slightly angled toward the driver's side of the head to assure they meet the water jacket in the head. Scroll down in this post, and you will see a diagram showing the angle of the holes drilled in the head:
848 "Steam Hole" Drilling Angle
