ARE YOU SERIOUS DUDE!? Put the crack pipe down!!

It takes a real moron to spend 4 grand on exhaust manifolds for an A-body. Maybe for a 70 Hemi Cuda, maybe.
Hemi exhaust manifolds (and maxwedge)are reproduced. M-code 69 440 a-bodies arent. Believe it or not, $3600 is not an unreasonable price for the 1969 440 a-body version. BUT, the ones in the op's referenced ad are 67 383. 10-15 times more common. Maybe worth a quarter of asking price.
(There were MAYBE 300 set of the 440 manifolds produced, not used on ANYTHING else by mopar, ever. They also were described in every magazine at the time as being super restrictive. So, how many set got thrown in the trash, for headers? How many left?)