Hey Calvin
The OH-6A is significantly different from the MD500/AH-6/MH-6, in that it has a different tail (V-tail versus the T-tail on the MD500), and a four-blade main rotor (five blades on the MD500).
There are also some other exterior and interior differences.
I suppose if you're in the mood for major conversion work, it could be done. But it sounds like a lot of work to me.
Quintin