Using a casting number 848 head on a 261 will result in somewhat higher compression, but some extra coolant passages need to be drilled in the head to match holes in the 261 block. A 261 head would be a drop-on fit on a 235, but the compression would be lower than with a stock head.
Jerry


"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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