Didn't all Twin Mustangs have Allisons?
Sorry. I suppose I could have worded my idea better.
I was hinting at a tank-busting Twin Mustang derived from the early Mustangs (Mustang Mk I/IA, Apache/Invader...). I said "Non-Merlin Mustang" and meant
early Mustangs, as opposed to
later Mustangs powered by licensed Merlins.
That said, I typed that answer while going all-out on a stationary bike at the gym. That's my excuse and I'm stickin' to it.
I have two Italeri 1/72 "Mustang I Razorback" earmarked for such a what-if. Might not be just for tank-busting, but could also be useful for anti-shipping missions.