I am very happy to see with what ease people these days routinely scale up models and repaint them. Very encouraging! I very much like your choice of model, with the history attached.
As for the Cirrus engine:
1) Bernie did a pretty detailed Cirrus engine for his PSW-50 build a while ago. I remember searching out a couple of photos for him that could be used. See
this post and the following.
Rereading that section of Bernie's thread I didn't remember doing all this work. Seems to be a goldmine, I'd have to say in retrospect. Here's
a kind of drawing that might prove helpful:
2) There is a
GPM model of the Gipsy Moth. Underneath the engine cowling it actually contains a pretty detailed Cirrus engine (I have the kit, so I can vouch for it), including individual cylinders and modeling each cylinder cooling fin. Should be good for you, if you'd care to invest in the model. If so, you would get two splendid models to build to boot...
The GPM engine model isn't so good on the crankcase however, so perhaps you'd be just as well off modeling the engine yourself. You obviously have the competence!
Leif