The 10″x15″ cylinder is made with 3/4″ bolts “caps” at each ends.
The front and rear caps are temporarily identical. The rear cap is of course supposed to receive/host the valve gear hardware.
A lot of work to do for this part, because the cylinder will be “made” with half-saddle as cast-in-one as it is the common practice in fabrication (and therefore presumably the CK Holliday was built following the same practice).