Please help me decide

Im not tired of my little mini but i want some speed and what better way to get it then to go import...but im about to talk to this guy about his 1985 bmw im not positive on what model it is but all i kno is that its 6 cylinders if you have any idea what model it is please tell me and also the miles are around 155K please help me all you can...as soon as i find out the price and other spec. i will post them. i want to get a good buy and not get jipped. thanks

sorry, can't possibly tell which model it is if all i have to go on is that it has six cylinders. Is it a 3, 5, or 7 series? engine spec needed too