A 318 can run very nicely with decent power. But ANY engine is basically an air pump. For performance, you need to get air in (carb and intake) air through (heads) and air out (exhaust manifold/ headers and exhaust).
I will assume your 318 is mostly stock and that you are driving this on the street.
Bottom line is in the "air out" part, your 318 can benefit from a good set of headers and dual exhaust.
1) Headers:
MANY small block headers route three of the driver side tubes below the steering linkage. See picture below:
View attachment 1560942
I DO NOT recommend headers like this, as the three tubes below the steering linkage sit really low, create clearance issues and regularly smash into the ground. Find headers that route differently than the picture above. Also, for your 318, if you have a choice, pick headers with a smaller rather than larger primary tube size.
2) Exhaust:
The good news is for a 1970 Satellite, you will have lots of choices for exhaust and there are kits readily available that will make installation easier.
I suggest getting a dual exhaust with 2 1/2" exhaust pipe (mostly because 2 1/2 is readily available). I also suggest getting a system with an X-Pipe (rather than separate exhaust pipes or an H pipe). An X-pipe helps with torque and your 318 can use any extra torque you can give it.
3) Mufflers:
This is a very personal choice, and there are many available. Some make your car sound like a race car, while others will be relatively quiet. It is all in what you want.
One potential place to look is at Pypes exhaust systems or Accurate Exhaust. Both make good systems for these cars. I'd talk to some representatives at those places to get suggestions on mufflers depending on your goal for sound.
Good Luck!