Jamie
Those are actually good running engines. A little heavy.
(basicly)All internal parts same as Red Heads except piston is Dykes ring in this later version.
The O.D. of the sleeve/liner is different but can be adapted to the Red Head.
When time allows am fitting up a Dykes ring top to go on Red head case.....I need more hands

The size is on the mounting lug but don't see it in the pics.
David