J Body verses B Body

I have a 80 Cordoba with a police 318, 4Brl engine. Only 80K. I will be installing a 511" Wedge. I was wondering what B Body (or other) this car is most like. I need headers that will fit with this 440 type engine and also a 408" small block. I am a 71 year young Hot Rodder. What rear end will bolt in? I brought this car from socal when I moved here. I used to work at Melrose Motors in Oakland. No problem building engines and Torqueflites. I used to race and I have built the engine and trans for many a racer. Once held the A Stock Auto record with Terry Esslinger's 64 Plym 426 Max Wedge.
This is called a "J Body".
Thank you all for your time.
Joe Mac
joemac1j@msn.com:confused: