I think this one will stay as is with the R-2800. It will be a low-level optimised fighter-bomber (no need for the turbocharger that way).
For the annular one (off to ebay), I have a couple of candidate "conglomerations" of parts. It won't be exact, just reminiscent thereof. I'll post pics sometime this weekend to see which you guys think works best. If anyone comes up with a piece/part/something that might work in the meantime, please let me know.
Pablo, I'm planning one with a ducted spinner (is that what you mean by inside the fairing?). That will be a contra-prop if I can find enough identical propeller blades.
I'm on a bit of a Seversky/Republic kick at the moment.