68 Baracuda 318 Exhaust manifolds.

Are the manifolds pure junk on these 318s or do they flow even some what decent. I recently picked up a date code 1968-3 318 that appears to be recently redone with an aluminum Mopar dual plane intake and Carter AFB 625cfm carb. was planning on keeping the 318 for a 70 Duster project that will be a daily tooter. Any suggestions? I don't want to run headers on this car, and the motor is complete ready to drop in.