Well I had to go 4BB because the 2 BB would not fit the Edel intake, and I had to change the intake because the original one was such in apoor shape. It's the one with the early egr, there's a chamber inside the top of the intake where the exhaust gas go in, and there's two little tunnels going straight up to the base of the carb. Clever, but after 30 plus years, the thing was so clogged with charcoal deposit that it blew that chamber plate inside the lifter valey. I tried to save it by cleaning everything and rivetting a new base pate, but I had to much intake leak between the heads and the intake anyway. I junked it.