My /6 - 318 exhaust was; Hooker headers and exhaust from jegs.
Headers were at the time $159 and the exhaust pipes were $200. Mufflerless systems were/are at Jegs and then the muffler price of your choice has to be added in.
A quick search at Summit racing turns up Hooker headers for a 400 A body @ $510 for fenderwells, painted, $760 coated, then add $195 for the 2-1/2 or $249 for the 3 inch kit, minus $20 for the mufflerless 3 inch kit. ($229)
Coated header, mufflerless system (There mandrel bent, clamps surplied or you weld) and mufflers are what you pay. But the total without mufflers would be;
760 + 230 = 1100 Save $250 with painted headers (?) = $850 or $20 more with there mufflers. $870
Another 2 hundred or less for mufflers?