There is a difference on the engine side housing only. The engine side housing on the B/B gives you more room for the heads and exhaust manifold. You can find repos. for aroung 75-80 dollars. The evap. tube that holds the POA valve curves to the fender on the S/B and the curve goes to the engine side on the B/B.
That's if you want to make it correct. You can use the same evaporator.
69 Coupe LeMans-Blue
Frame-Off Resto, ZZ-502/502 Crate, A/C, Griffin Rad., March Serpintine Sys., 2800 Stall with Hughes T-400, Currie 9" with 370 Gears. www.geocities.com/mobiletools1/