For a non-power steering (EHPS) MR2 with a manual tranny, the alternator is rated at 70amps. For an automatic non-turbo MR2, the alternator is rated at 80amps. EHPS (Electrical-Hydraulic Power Steering) is run off of electrical, rather than hydraulic power, so any power steering cars are equipped with a 100amp alternator.
MR2 alternators tend to be fairly durable units, but do fail. You will probably note a loud "death whir" coming from the alternator for several miles before it fails. An idiot light should light up on the dash as well if the alternator has failed or is at reduced output.