Ok fellas...318 help needed , Mpg , reliability and enough power ***for a big boat !!!

I would pull the heads for no other reason than to get hardened exhaust seats installed and a valve job done. While they're off, I'd have 'em milled just enough to get 'em flat--not looking for a compression bump, just an excellent gasket surface. New valve seals and a set of fresh springs (nothing fancy) would be a good idea while they're off.

I wanted something similar out of my ex-fiancée's '85 Fifth Avenue, pretty close to your car in weight. I installed an Edelbrock 2176 because I had it, and a ThermoQuad from a '77 truck 360 topped with an '84 Gran Fury AHB air cleaner. I'd have preferred a stock spread-bore intake but didn't have one. The rear axle was swapped from the 2.26 geared original to one with 2.94s, and the ESA was ditched for Chrysler electronic ignition using a junkyard harness and a distributor pirated from a '73 340. I replaced the heavy advance spring with a lightweight MP one. I never touched the camshaft or stock exhaust, yet it was a totally different car. It was much quicker than I expected, having driven it before any mods. I really didn't want any more out of it but had I done the cam, I'd have probably used a stock 340 replacement. The 2.94 gear is perfect with an A999, something Chrysler knew when building '80s cop cars. If the car were still around, I'd use Magnum exhaust manifolds (preferably '91-'93) and 2.25" pipes with quiet mufflers. As it was, though, it consistently got ~18MPG if you could keep her foot out of the water pump (not easy--absolute power corrupts absolutely :D).