I think you'll find that the Crane / Allison unit is sealed in epoxy. Not
very servicable. On the other hand, at around $100 a crack - it's not too
much of a strain on the budget to carry a spare. Unless you are like some
of us that keep a set of points handy in the "spares" kit.
I can't speak for the Pertronix.
It should be pointed out that these systems are pretty reliable, and any
failure of them could be attributed to other problems.
Go for it - buy one... errr two.
With the Crane unit... saving up for Electromtive. Hi John!