As far as working over your 360 is concerned, yes the heads would be a good place to start - magnums are nice, but keep in mind that they limit your intake options should you be planning to do this with swapmeet/ebay parts, and the factory intake you show in your pictures certainly won't work. There are plenty of other iron head options that will yield improvement - including doing some work to the heads on currently on the engine.
I would start by doing something to free up exhaust flow. Headers specifically, and perhaps bigger pipes if the car has tiny duals in place - don't go crazy with pipe diameter tho - oversize pipes will actually hurt performance. Determine your goals for the car and have the exhaust done accordingly. A competent exhaust shop (not a chain store) will help you choose the right pipe size, headers and even mufflers for your targets. Also be careful when purchasing "performance" mufflers. The interior drone inside the car when being driven on the street or to/from the track will make you nuts. Keep in mind that you can always "uncork" the headers at the track, tune for the strip and then close the exhaust up again for the strip.
As far as camshafts are concerned, if your short-block is in good shape, and you plan to keep it as such, compression limits how radical you want to go. Factory spec 340 cam or something like the comp magnum musclecar cams are as wild as I would go - but it's best to contact the cam manufacturer and tell them as much as you can about your combination, then go with their recomendation. Comp is very good for this. While you are swapping the cam, make sure that you replace the timing set with the 340 double roller chain and gears at the least.
Another simple factory thing that will gain some power & reliability would be the addition of the 340 windage tray. It's available from Mopar Performance and is pretty easy to install.....when the engine is out of the car.
Lots of other simple things you can do without having to build a "monster" motor to gain improvements at the track, like losing the rubber -isolated leaf springs, etc...
