O2 sensors- 3wire and 4 wire.

I've got 4 wire O2 sensors in my car right now and the female (vehicle side) only has 3 wires because it's an 89. So the missing wire is the heater ground I would assume. I'm running rich and I'm sure that these are the culprits. They only read .1-.3 volts on my B.O.B (which is lean).

#1 Can I just ground the missing wire (Heater ground I think) to the Ground of the O2?

#2 I do have a set of 87 3 wires that look to be in great condition but the hardshell is different. How can I test the sensor so that I can repin them to the 4 wire hardshell?

BTW, these sensors were in the car when I got it- this was not my ghetto fab idea.

Any help would be appreciated- It's nice outside and I want to drive it without smelling like I work at a gas station (because of the smell of the gas not because the people who ...nevermind).

So check between the signal and ground when heating and look for voltage or power it up on the bench and read between signal and ground with heat?

I physically checked for vac leaks and even capped as much stuff off of the tree and intake and didn't get any response. I even checked with carb cleaner

The sensors generate their own voltage so I shouldn't have to power them up to test... Let me know- I dont want to fry anything and my wife will make me sell the car if I ask for another forward on my allowance for something silly like new O2's.