I just found a 73 challenger rallye and it has a 340 in it. I was thinking about swapping it for a 440. I plan on making this car a sunday driver but still have enough power to take to the track. I don't mind spending money on it, although the more it will cost the longer it will take to get it.

Also, its all original so I kind of feel bad about changing the engine, but I want max power with it. Thanks.  

It all depends on how fast you want to go, however if this is a numbers matching 340 car, then I would rebuild the 340, this will help keep the value of the car. 340's can make tons of power and are capable of pushing a e-body down a 1/4 mile.
In fact if the 340 has decent comp. and good oil pressure just use the bottom end as is and start by adding performance parts. Have a plan so when your finished you won't have to redo work.
Ideas, headers, cam, intake, carb, MSD, rebuild the heads, port & polish, aluminum rockers, high stall converter, gears.  

I really don't know much right now. This is my first project. All I have worked on so far is my pickup and its and 04 ford. Completely different. Anyway, I have a couple of mechanic friends who are gonna help me out, but I'm trying to learn things for myself.

I'm trying to make this thing as fast as possible. I want to KILL the kids in town with their little civics (there's a bunch in this town). I have been looking at the 6 pack intakes, what would it take to use one of these?  

Six packs look great, however if you want to run fast you simply won't beat a RPM air-gap intake with a 750 double pumper. The 750 is one of the most street strip friendly carbs period, very tuneable and simply #1 pick among drag racers with a street strip combo.
Don't worry about the ricers, a strong 340 will beat most big blocks.
Another option is a 360, or a stroked 340 or 360. Stroking a 340 you end up with 416 cubic inchs.
A stroked 360 ends up with 408 cubes.
My theory with performance is KISS, keep it simple st___d.
My current street strip combo is a stoke bore 360, 9.5 compr. 360 LA J-heads, ported & polished. Solid lift .528 mopar cam, 1 5/8 ceramic headman headers, 750 D.P. air-gap intake, 9 1/2" converter, 4.30 gears. Runs 12.6's at 108 in a B-Body Satellite.
If I put a stroker kit in with a different cam the car would run 11.90's in street trim.
All this with a street friendly small block that gets better fuel economy than a big block and better handling all around due to less weight over the front of the car.  

You can kill the kids down the street without killing your self in the corners with a stroked 360.
You can build your 440 and do the same straight line but might wanna think about some suspension upgrades.  

OK, this is probably a dumb question but which crank do I run to stroke it to 416? Also, the RPM air-gap is the edelbrock right?  

You get different cubes with different bores from the 4' stroke crank like say the bore of a 360 at .020,0.30,.040,.060=406,408,410,414
or a 340 at .020,0.30,0.040,.060=414,416,418,422
360 std bore=4.00
340 std bore=4.040
There is a 4.1 crank available used with 6.2 length rods=425ci, call ohio crankshaft.  

A 416 is a 4" stroke crank and a .303" over 340 block.  

Thanks guys.