How much HP from a neglected, full of patina, non-cared for, a late 73+ is a stock 440 vs. a '71 318 ? Didn't stock HP numbers drop after '71 ?
Well, that's a tricky question to answer.
First, the 71 horsepower ratings were Gross ratings, meaning the power produced by a bare engine (no accessories), running on a test stand, using headers, and with corrections made for atmospherics... which essentially means the power output under ideal conditions. Starting in 1972, automakers started using Net ratings, which means an engine running with all it's accessories and no corrections being made. So 1972+ ratings are much lower than 1971 and older ones. For example, a 1971 318 is rated at 230 HP, while a 1972 is rated at only 150. A "Net" 1973 440 is rated at 275 HP, but if it were "Gross" it would be around 335.
Another consideration is there aren't a lot of stock engines to be had anymore. Most engines have been rebuilt at least once and modified God knows how many times. I bought a doner car that was a rusted out... and I mean rusted OUT, 1973 Chrysler Town & Country wagon that had been sitting since the owner died about ten years ago. This thing had sat so long the water pump had corroded into a solid mass. But, the engine turned, which was what I needed. What was odd was his neighbor, who had inherited the car, told me the previous owner used to race this thing out at Jax Raceways, which I thought was BS until I saw the Stewart Warner gauges and B&M shifter inside the cabin. I put the drivetrain in the Roadrunner, took it out on the street in front of my house, floored it, and left about 40 feet of rubber there. I don't know what was done to the engine, but it's putting out a LOT more than it left the Chrysler factory with.
As for weight penalties, yes, a 440 is a lot heavier than a 318, but what will you be using the car for? If it's a sight & sound machine, i.e., a cruiser that looks good and smokes the tires, then who cares about another 200 pounds.
If you're taking it out to drag strips for serious racing, then you aren't going to be racing it with a 318 anyway.
But... even a 1973-74 440 can be nicely bumped up by adding a set of headers, a good aluminum intake, and a decent carb. That'll get you close to the Net for a 440 HP for much less than what it would cost you to get a 318 up there.
any luck with the door ?
After it was removed, i cut it at the kink to see just how closed off it was. 
