MCI [ATM overhead]

  Line Rate 155.520 Mbps
  Available to ATM 149.760
  Available to AAL 135.632

The reader can apply their favorite packet size distributions to these
numbers.
Having said all that, I am not sure where that leaves us.

That leaves us with the throughput of two DS3 links. It doesn't seem worth
the effort given how short term a solution it is.