Hello,

How about this:
Black Locust for mud sills & pegs - rot resistance, easy to split
Sugar maple for all braces - compressive strength
Hickory for beams and joists - tinsel strength
Ironwood is a name used for different woods in different places usually referring to a type of wood that is a lot harder than the predominant wood species of the area. So I don't know exactly what this means in this case.

For vertical members, or posts, a mixture could suffice.

Greetings,

Don Wagstaff