Problem is, Erik,
that the case bolt just below rear of rear cylinder on K cases is in the wrong place to make a stroker, being too near the crank, see my photo.
That bolt was moved higher (to the same location as the one opposite on the front of the front cylinder) in 54 to make the KH cases that needed deeper slots for the longer stroke…
Never check it cause my XLR is a stroker as well, but maybe more likely, the big eyes -54R rods need more clearance and someone tried to mount these in the earlier cases in question…
We need better pics!!!
Patrick