O2 sensor compatability

I would like to know if the forward O2 sensors in a 99 suburban,with 5.7 (350) engine, are the same as the rear O2 sensors.The parts store shows two different part numbers,but can they be interchanged???Would the electrical connection be different???Thanks for any input.
chuck's

They are different.

Thanks.Any idea what the differences are???
chuck's

I'm not sure but if they were the same the parts store would not have both listed. They could save by only having the one.