6. My core I bought came with a set of A-body big block exhaust manifolds. From what I've read these are about the best fit option out there but do limit the performance. If they will keep me from being able to get to that 400ish HP mark, then I'd likely sell them and put the money toward a set of the TTI headers.
The ones in the picture (of everything spread out) don't look like BB A-body manifolds to me... but the real thing is going for low four figures (383) and even more for the rare 440 ones.
Are you sure someone actually gave a pair away with a core engine? If so, sell them and you can not only buy headers but some other parts too!