Okay, gotcha.
I'd like to counter with this idea, however:
G10 was developed into what eventually became the K4. It was developed in a relatively short span of time, as well (both G10 and K4 are '44 planes). There is a top speed jump from the early G10 to the K4, but for the most part there's nothing else that's changed.
2 planes, identical in construction, and performance, the one being 20mph (?) slower than the other. I'd suggest logically that we just pick one of them. If I had to just pick one of them, it would be the one that is slightly faster. So I'd pick the K4. They're from the same time frame, so there's no role the G10 could play that the K4 could not substitute.
I say use the K4 for anything that would require the G10. It's already got the speed of the best G10's.
It's the same time frame, it's almost the same plane, I'd say just use the K-4, which if it isn't perked now probably won't be perked in the future.
My $0.02, as I'm generally a practical person, is to pick the better of the two and drop the other. That is, pick the K4 and drop the G10 (with whatever G10 stats you pick to model it as)