Allison 3 information, please

I am using my 1976 vintage, re-furbished Allison 3's as a stop-gap while I decide on a replacement for my Kharma 3.2 FEs, just sold. I am driving them with Atma-Sphere MA 2.2's, and need to know their impedance and sensitivity, as a guage for how my amps will drive difficult loads. Can anyone help? Thanks.
P.S. They sound phenomenal!!!! Too bad they're extinct.