Some years back, I got the impression that as other race trans shops started to proliferate, B&M kind of pulled back into mostly RVs & towing, but I could be wrong.
Back in the day ('50s - "70s or so) they were hot stuff. I guess the question is which type of trans is it, and does their website have any info on what's inside?
A used trans IMO should always be looked through, if only for peace of mind.