beefing up the stock 318 engine CHEAP mods

First of all welcome!

As for your 318;It will be a 2 bbl unless someone already changed it. The cheapest upgrade to 4 bbl would be a cast iron stock intake and a thermoquad carb. Lots around on 360 powered trucks/vans and some 80's era 318 cop cars (Diplomats etc).Some late 80's 318's had rochesters as well and a good casting head called the 302. Make sure to get a 4 bbl air cleaner filter and housing. A K&N air filter is inexpensive,and reusable.

Dont bother upgrading your ignition system. Not much gain per dollar there.

Summit offers cheap headers,dual exhaust kits and cams. Your mopar is an A body. And yes it's fair amount of work to install headers. If you change the cam,do the timing chain. Upgrade it to at least a double roller. For a few more bucks you could add a tensioner. Wont help make power but will ensure accurate cam timing when the chain starts stretching.

Another cheap upgrade would be a thinner head gasket. Buy an .028 thick Mr Gasket head gasket. A bit more compression will help.

Transmission shift kits are inexpensive too and simple to install.

A distributor recurve kit is another cheap upgrade that will help. Or grab a used one from a small block pickup/van. It will have a bit faster advance curve and lighter springs.

If you can port and have the tools,that will definitely help quite a bit and cost you almost nothing.

Rear gears would really help,but probably be more expensive than the other mods and I have no idea what you have for gears/diff.

Good luck!