So here are the bits, what do you think it is ? OK, some of it's covered up (I was painting when I had this silly idea) anyway, it would be too easy all uncovered.
OK, maybe you need to see all the bits together.
If that doesn't help, these exhausts might just do it.
You're all just too good. Yes indeed it's an R-2800. Wiki lists about 34 different aircraft that use this engine in one form or another. But the Merlin has about 40 applications listed.