Without having the time to read all of the other responses, I agree with Phil in part and strongly disagree!!!
Where I agree - The problem is that 80 - 90% of the dists we have tested recently, off of running cars, are bad. The bushings are worn out and there is significant shaft play. This is the single most common performance problem on old Volvos that we see in the garage. And not having accurate timeing causes all sorts of problems, including overheating. INstalling the types of electronic ignitions discussed where the points are replaced will cure a moderately worn shaft problem as the system does not rely on
the mechanical accuracy of the shaft and cam movement.

Where I disagree is that beyond curing the worn out dist problem, the type of ignition that many or you should be considering is a knock sensing, ignition retard system. A lot of the b18Bs at 10 - 1 compression and the B20Es at 10.5 to one have problems with detonation using todays unleaded low octane fuel. This leads to the thick head gasket fiasco that gets rid of the detonation but kills the power and destroys combustion efficiency. Now there is a really nice solution available that lets you run high CRs, even higher than stock, on low octane. The knock sensing ignition modules use either a delco or Bosch knock sensor screwed into the block, and take only a couple of other wires to hock up. When there is any detonation or ping the ignition timing is retarded just enough to get rid of the detonation, and than lets it go back up as much as possible - all done in microseconds. This is current tehnology and is why the CRs on modern cars are back up to the 10 -1 levels that they were in the 60s. Its part of the reason for the high outputs from modern 1.6, 1.8 and two liter engines, maybe more that the Vtech and DOHC. The electronic ignitions most people are using are 1970s and 80s technology.

John
V-Performance.com