On looking at the range I'd like to monitor (1-50 Amps), it appears that the Allegra link Reloadron offered would be the better solution. It's about $8.00 but has a reasonably linear result and can work with unknown polarities. From what I can tell the resolution is about .05V per Amp which works out to about 10.24 bits per amp (5VDC ref). +/-50A = +/-512 bits (10bit adc) around the 1/2Vcc zero current datum. I should be able to directly feed an MCU ADC input.
I found the IA pricey ...relative to FREE from the OPA I have, of course accuracy and precision will suffer. I wouldn't need a full swing to the Vcc rail, so the 33171 could work in a more limited way. Reloadron gave useful advice , which I will take.
I buy mostly from Newark or Digikey.
Thanks for the help!