I’m a noob here, so I would appreciate any help or advice.
I just bought an 89 pickup, it currently does not run right.
The previous owner said it was getting hot, so he had new heads, valves, camshaft, plugs, and wires put on. This was 3 years ago and it has not ran right since. It stumbles and will not go over 5mph.

The previous owner said the mechanic said He thought that the motor had been replaced and he thought it was a 93 motor? I don’t know if there is a real difference between and 89 and 93 v6, or even if it really is a 93 motor?

How can I find out what motor is actually in it? Where would I look on the motor for the engine tag to identify it to be sure, and where could I input the engine tag to identify the motor?

Could the issue be the timing, wrong timing belt due to wrong year of motor, wrong heads, or camshaft due to wrong year, or bad fuel pump?
I appreciate any help.
I want to get my new baby on the road before winter.
Thanks!

 

Welcome!
89-95 3vz are all the same mechanically, and to my knowledge there's no way to know what year one was made. The only real differences would be in the engine management system (ECU, sensors, wiring harness), but I'm fairly sure even those are mostly the same.
It sounds like it's time to start troubleshooting. Find a fuel pressure tester and a timing light, make sure both are within spec. Check to make sure the plug wires are connected in the proper firing order.
Your problem doesn't sound mechanical to me, so you'll have to go system by system to find the problem.

 

Thank you very much. I will start by checking the plugs and change the fuel filter, and check the fuel pressure.