I got one of these--Manfrotto sells them separately--and mated it with a 486 without a plate adapter. Manfrotto sells most of their heads this way. The plate adapters simply screw into the ball heads. This way you get the QR plate-head combo that suits you. BTW, QR=quick release, sorry.
http://manfrotto.com/product/8374.56.76907.0.0/625/_/RC0_Rapid_Connect_Adapter_with_030-14_Plate
I like the old school hex plate for the RB67--max contact area for secure grip without tightening the crap out of the plate screw.
Love the SQ-B. It's a stripped-down SQ-Ai. No electronics apart from the shutter, so the metered finders and ISO dial backs of the A and Ai models can't talk to each other on the B. Takes all Bronica SQ "S" and "PS" lenses. No "T" exposure but does have a "Bulb" setting for long exposures. I wanted a manual 6x6 format SLR and this was the "one." Light, compact, basic square format kit. They're usually very affordable because they're totally manual. Just add a light meter and you're set!