It's going to be a gamble trying to get 2 different size rims and tires mounted to be exactly the same diameter. Even the same size tire from different manufacturers is going to have different out diameters.
My suggestion would be to get the same rims and tires, but get the offset of the rear rim in a smaller offset. That way you're getting the same size wheel and tire, but you still have the staggered look. There was a brand called AXIS that made rims like this called the "Maxxis Lip". They had a bigger lip in the back than the front to simulate the staggered look.
Another option is to run some spacers in the rear to poke them out some more. Essentially this is reducing the offset of the rim.
Or, weld the center diff and take out the front axles and then the wheel diameter doesn't matter. It'll be RWD at that point. There's a lot more to it than that, but you get the idea.
Good luck with it, and post some pictures when you get started on it.