[ItBites]

Chassis or engine dyno?

For chassis dyno:
Pro Dyno can do this sort of thing. Not too sure about two O2 sensors (however if you're carbureted, with open plennum manifold, side to side differences should be minimal). I have a friend that has his pro miata there every so often. Just make sure the normal dyno operator will be there. Sometimes there is a younger guy who doesn't know as much and has trouble.

For engine dyno:
Basko Engine Service. Jim Basko is first rate and does another of my buddies' blown alcohol dragster motor. Years of experience...

Good Luck