So is there somewhere special to buy, say, the o2 heater relay on my 89? Or should I just take it down to the auto parts store and have them match up a regular Bosch relay?

Regular Bosch relay will do you just fine.

Sensors are another matter. Several of them are very, very picky. You want NGK or Mopar only for the O2, crankshaft, camshaft, TPS, and MAP sensor.

Thank you sir!

The cool thing is, if you suspect one is bad, swap it with another.

Thanks Cruiser, I have done that, just thought Id pick up extra.