Having just done a complete rebuild / balance / blueprint on a friend's 5.7L
Crusaders, I can add one more item: The pistons have to be mounted on the
rods pointing to the back of the engine on the counter-rotating unit. This
is because the pistons are slightly asymetrical, with more material and a
stronger skirt on the side of the piston subject to side-thrust when the
cylinder fires. Your engine will not live very long if you do not do this.
Terry