the differences between flowtech and bbk is for on flowtechs driver side is a two piece design which is what makes the instalation easier. the bbk is a one piece and tuck up agains't the block and the flotech wrap around the steering bbk is tucked behind it. which vorh are good and both are bad. then flowtech has your standard 3 bolt header flange design bbk is your bal knuckle style two bolt. again both are good but I find the flowtech to be more universal in the part I like both. But I love my flowtechs!!