For the speedometer, it sounds like you need to get an entire speedo unit (or even a used cluster) from one of the ebay sellers. At least one of them is in the business of selling speedometers that he has reconditioned himself.
For the lack of spark: You probably need to get a manual and try to figure out which ignition system you have whether it has a diagnostic connector. Around the 88/89 time frame Volvo changed to a more sophisticated ignition control system called the EZ-116K. The spark timing is controlled by an external control unit, which gets signals from the Fuel system controller, a knock sensor, and other sensors. There is an electronic goody called a 'power stage' that fires the ignition coil. This system has a diagnostic capability, with a small box under the hood for the purpose. Ours is a 1988 240, which still has the earlier type system, not the EZ-116K.
There should be a VECI label on the drivers side strut tower, telling you which motor you have. I suppose yours would have the B230F engine.
I have the Haynes manual, which doesnt have as much detail about the electronics as I like. I think the Chilton's manual would not be much different. There is a thicker manual published by Bentley that is supposed to be better. You can usually find such manuals for sale on ebay. I know that Volvo also sold manuals, but they are harder to find now and cost the most. My personal opinion; if you are going to own an old Volvo, you will be much happier having a manual and being familiar with it.