We have the same width tub as an M416 and our hubface measurement is 55.5". With Ford Raptor wheels that have 6" of backspacing and 2" wide adapters; the 35x12.5 BFG's sit right at the edge of our 12.5" fenders. See pictures below.
Will you need to run an adapter for your Toyota wheels? If not, do you still need to run a spacer to clear your centercaps?
If neither, then I'd say your axle width should be ~58.5". If so, then 1.5" spacer/adapter should be ~55.5", 2" spacer/adapter should be ~56.5".
I think I got that math right
. If you can, it's best to lay everything out with an existing axle just to make sure all the approximations are correct and they are fitting the way you want.
Hope that helps,
Josh