What you have is a Holley Electronic Distributor as Trevor mentioned. Your Scout was most likely built in 77'. You're missing the gauze on top of the spider clip, which I can see. Your unit looks pretty clean. The magnetic pickup assemblies are rather 'problematic' only in the case that they are 50 years old with no replacement. They can have issues with heat, age...etc. Many people upgrade to a
Pertronix Conversion System which is a 'hall affect' senor. They are a nice upgrade over your system. You would need a matching coil to pair with it. I would start with what I already mentioned about the lubrication and service of the advance plate system, reassembly and unhook your vacuum advance and measure your timing at idle and certain RPMS with a dial-back timing light to see if the timing is moving around. If it is moving around, your ignition system is likely to be at fault (your original mag. pickup assembly). I would consider a complete teardown of your unit, including the distributor drive gear, and clean everything and lubricate and reassemble. If you remove the drive gear, you need to note the orientation, as Holley units were hand drilled and the hole is not straight.
Edit: I didn't read you had already installed a Pertronix. I wouldn't rule out it being the problem UNTIL other avenues are checked.