alternator will not make it miss . If you think it's the alternator , take the battery cable off of the hot post and see if it keep's running . If it go's dead it's the alternator if it don't it's good .
If the car is from 1962, yes that is the case.
On any car made since... about 1980... this is NOT A GOOD IDEA, especially on this Cadillac which probably has at least a dozen computer modules, any of which can be destroyed by a voltage spike that results from this kind of dangerous practice. It "IS" possible for a charging issue to cause driveability issues... I've seen it a few times due to a bad diode or voltage regulator.. one way you can test this is to just unplug the electrical connector for the alternator and drive it (make sure the battery is fully charged prior)... but I don't feel this is likely.
You mentioned the voltage is jumping around? Exactly what voltage values are you seeing? Anything between say... 13.0 to 14.8v is pretty much acceptable... this is going to vary somewhat based on engine RPM, electrical loads, mechanical loads, etc...
As for an injector issue... not likely for an engine with multiple misfires. There is an injector for each cylinder, and chances of more than one going bad at once is next to nil. Also, any problem in the injector circuit itself (including an injector that is electrically stuck shorted or open) will set a separate fault code.
Some do have a good point though. If you can obtain a scanner that will display live readings, including individual cylinders' misfire counts... then you can drive around and have someone watch which cylinders are misfiring the most... this could at least narrow it down. If it's always the same 2 or 3 cylinders it's likely only a tune issue, whereas if all eight cylinders are triggering misfires, it could be a timing, fuel supply, or electrical issue. I've also seen a plugged catalytic converter set misfire counts, but this would be all four cylinders of the same bank (i.e. #1,3,5,7 or #2,4,6,8)
