I did some looking into this a while back, not too sure on B body's, but for E's,in 71 at least - should be the Midland Ross - my cuda had a MR on it when I got it in 1994, it failed a few years later and I found a Bendix - which is painted black in a parts warehouse near where I worked - had to give the MR as a core. Frank Badalson in his monthly column a few issues ago in MCG stated pretty emphatically that the MR is 71, Bendix for 70 - if I remember correctly - I just scored a NOS in the box MR booster 2 months ago on ebay - and I was looking for a long time for a nice MR - ramman advertises the Bendix as a 70 and MR as 71 too. Have seen both styles on B/E body's over the years also - but I'd be leaning on Bendix 70, MR for 71 from pics I've seen over the years and I've collected of original equip. cars -
but Frank does know quite a bit - be interesting to see what other's say