Your temperature sender (circled in photo) is of the electric style rather than the original capillary tube design, not necessarily a problem since it looks as if some of the guages are also later replacements and the two could be properly matched.
You have said the engine is a later replacement, it is definitely NOT an original 216. It is a later 235 or 261. Indicated by the style of water pump, completely in/on the front of the block, not covering the block/head joint and also being inset in the block rather than completely on the front of the block. I am not sure, but think the unequal size pulleys may be normal for that style of water pump. Others can confirm. Also ndicated by the valve cover being held on by screws at the lower rim rather than 2 acorn nut on top. The Rochester B carb is consistent with these comments. Its smooth inlet is suited for the CMP slip-on air cleaner (compared to the later variants that were set up for an air cleaner held down by wingnut). Have you looked at
www.stovebolt.com and
www.inliners.org for engine information?