Chris, thanks for looking that up.
So... didn't the 948 run the DM2 distributor? Does it use the same points as the 25D4?
If the points fit, follow Jack's steps above on fitting the points. Pay particular attention to three things:
1) Make sure the flex-braid is in place between the breaker plate and the dizzy housing. It needs to be intact and flexible to complete the ground circuit and allow the vacuum advance to do its job.
2) Make very sure you fit the little nylon/plastic spacer washers on the spring arm of the points. Failure to properly fit those spacers shorts out the moving arm of the points... effectively creating a permanently closed kill switch... no spark.
3) When fitting the condenser, make sure its little forked spade lug on the wire is not touching the breaker plate or fixed portion of the points. As above, that will create a permanently closed kill switch.