Cheap and easy to go just use the pertronix and the old carb if it works well for you. If you decide to swap the carb out for a weber/5200 style carb you should forego the pertronix and upgrade to a Duraspark II ignition system. Running a DSII you can install any regular, non SCV carb that fits., Carter YF or RBS, Daytona Universal, Non-SCV Holley 1940, Autolite/Motorcraft 2100(1.08 or smaller) w/ appropriate adapters, ect. If I were you I'd wait until I needed a valve job and find a large log head in the meantime and do the swap at that time with a reconditioned head. Run the pertronix and 1100 carb until then. Be advised that you will need to surface mill the new head to match the chamber valume of you're head + another .025" to compensate for the thicker composite head gasket. You want to end up at 9:1 static compression, so mill accordingly or you will lose power.
As for what's needed to go to Duraspark II, here's some advise I've given before,
If you buy the distributor, cap, cap spacer/adapter, rotor, ignition module, ballast resistor if needed, plug wires and coil for a '78 Fairmont 3.3 ltr you'll have everything you need but the harness. Almost any Ford from like 75-85 will have the harness you need, 80's Jeeps also have the harness. You'll want to find a harness b/c a new one is around $130-150. Just be sure the vehicle had the module with the blue wire grommet.
If you can't find a harness you can get the coil connector, and both the 3 terminal and 4 terminal module connectors from Rock Auto under '78/Fairmont/3.3/Electrical-Connector. But I've never been able to find the distributor connector. You'll have to cut it off and wire direct or narrow female spades into the dist connector.
Distributor - A-1 CARDONE 302690
Ignition Module - MOTORCRAFT DY893
You can use other modules but this is the stock setup and vastly superior to what you have now.
You'll need this harness and make sure you get that other plug there.
This is the OEM diagram
Here is a diagram from painless wiring that is slightly different.
http://uploads.tapatalk-cdn.com/20140123/yqyda8ub.jpgPut some cam break in grease on the new dist gear before installing.