Micahel,
Since you have a low performance 1972 318, no reason to go 'crazy' trying to get
unwanted horsepower, and stick with improved low-end torque.
A good cam, would be the Compu-Cam 'High-Energy 252' (Part #20-208-2) which has
a lift of .425/.425 and 252* Duration, which is excellent for a stock 1972 318. Of course
getting the Cam Kit is highly recommended with (Springs, Lifters and Retainers, etc.)
Note; The 1972 318 (Stock Camshaft specs + .390/.420 Lift and 242* Duration)
Of course a new timing chain will be required.
A perfect intake would be the Edelbrock Performer #2176 - which is designed for a
street application where you will not be going above 5500 RPM's.
And an Edelbrock Performer #1403 500 CFM Carburetor will give you some good
low and mid range performance, as well as good Gas Mileage.
As for Cylinder Heads, the #4323302 castings would fit nicely, as they have
a swirl-port design and have 63.0 CC chambers which will keep your compression
close to the stock 9.23-1 (as the 61.0 CC 1972 Cylinder Heads). The #302 Heads
have hardened exhaust seats, so you can probably have a valve job performed and
utlize the current exhaust valves. Intakes, you may have to change to stainless units,
but stay with the stock size (1.78") as bigger valves will 'not' help you in the
low-to-mid power range.
The #302 Cylinder Heads have better 'Volumetric Efficiency', which allows the gas to
hit the chamber better, and dissipates the exhaust much faster.
As for exhaust, TTI units are fantastic, but expensive. You want to take a look at
Accurate Exhaust systems for a performance dual exhaust system, which keeps
a balance back-pressure, which is dynamite for the street.
Paul