I was told when planning to kitbash the Academy M998 Ambulance with a Tamiya HMMWV that it wasn't easy to do because the basic dimensions of the two kits were quite different.
I assume the same problems would arise trying to mate your Legend conversion to the Yamiya kit.
It's not a big problem though, just find a Academy kit, they can be found at very low prices.
Cheers,
Christophe