Read post 433.
These are bigger in proportion to the 440 being bigger.
Size for size the Magnum port is a modern more efficient port. The magnum heads is a closed chamber design. The best you can do to keep the heads apples to apples is to do some very basic porting . If you do this yourself it will be at minimal cost. While the valves are out you could back cut the intakes. You can't fix that your heads are open chamber and have no quench.
Maybe , but i would be willing to bet your 200,000 mile cylinder walls are in better or at the least no worse than your 440 cylinders including the one that was rusty.
You could do a compression test to see if you are down on compression on your 360. As good as it runs you may find the compression is still good. Have you done a compression test on the 440 yet? As far as compression ratio this is where the 360 has an advantage and if you want to squeeze more potential out of the 440 anything you can do to help it out would be good. But this will probably cost the most to fix. Use the thinnest gasket you can get if your budget doesn't permit anything else.
Of course you should change the stock rv cam from the 440. I'm not saying you should put the exact same spec camshaft in the 440 as the 360 but rather something that is proportionally the same as the 360 as a minimum.
The goal is to make 12.9 a smaller number. Right?