Dash readout gave following codes: PC1406; TC0035;TC0037;RF2560and PCM?

Range, <<< seen where? we cannot see what you see, here.
sorry.

wild guess transmission range fails on the cluster??????????
car drives ok, not told , job 1. yes/no.
well we scan the PCM (means OBD2 port on dash) scan TOOL.
and see why.?
causes are (but the error matters) DTC
1: lost comms from TCM to PCM and cluster brains.
2: transmission PRNDL switch fails but does car drive oK>?
3: wiring related to all that failing.
4: check fuses for blown?

A good chance that your car does NOT have one. OBDll was not required by law until 1996.
Some manufacturers had there own systems before then.
I found the following web reference:

"Sorry fellas, the 1989 XJS has no onboard diagnostics at all. It only has a red feedback monitor hookup [with a blanking cap] back near the fueling ECU in the boot. It was used for mixture setup and that's pretty much it.
The trip computer fault code readout didn't arrive until 1992."
The trip commuter readout he refers was a way to get codes (after certain steps taken) to show up in the trip computer display.
For OBDll compliant cars .... the port has to be within 3 feet of the driver with full access .... usually under the dash
Helpful?

The tach readout is controlled by software in the Instrument cluster (IC) based on the values sent from the VCM/PCM. The readout on your scanner should show the correct rpm values (120 to 240 is wrong). Therefore, if the engine is running normally, the computer is probably not sending the correct values to the IC, but the crank sensor is OK.

Code 12 means that the battery input to the PCM was disconnected within the last 50 key cycles (this is a normal condition).
Code 55 means that you have reached the end of the codes. This is also normal

So if you have a 12, 55 code readout, you basically have no error codes stored.

Here is a link that lists the code sand what they mean.

OBD 1 Codes DodgeForum com

Code 16 is no communication between the PAT and PCM.
This code can show up as a B1681 or HEC code 9681 on a dash test.
They all mean the same thing but from different detection points.
Cause is an open, ground or cross in the circuit between the PATS and PCM.

This is an anti-theft feature. The key you use has a radio chip (transponder) so that only the keys programmed to that vehicle will start it. If the key isn't present, then it won't start. Something could have gotten in there and chewed on the wires or the connectors could be loose. It is also possible the module is damaged (not as likely) but in either case, without the right dianostic equipment, this isn't something that you can fix yourself. Even if you swap out the module yourself, it still has to be programmed to operate with the car. The PATS module is built into the instrument cluster on this car. I suspect you may also has 'dashes' (-------) where your odometer readout should be.

buy manual

TCM and PCM, might be in the center dash under the radio area, but from the codes you gave, I would say it's more than likely a grounding problem causing communication problems.

P1260 - This, basically is indicating that a theft has occurred, and the engine has been disabled.If the engine stalled, during travel, and the code was pulled after the stall, this will indicate the following:

1.A loss of power, or ground wire to the PCM
2.A Faulty PCM power relay
3.A Faulty EEC power diode
4.A Faulty VERF signal.

Passive Anti-Theft System (PATS) communicates PCM through instrument cluster to enable or disable vehicle's engine. Within one second after engine start, PCM must receive an enable signal from instrument cluster or engine will be disabled. Along with enable signals, instrument cluster and PCM share messages that confirm security codes shared during initial installation. This shared security data makes instrument cluster and PCM a matched pair, so neither will operate in another vehicle. When system is functioning properly and ignition switch is turned to RUN or START position, THEFT indicator light will turn on for 3 seconds, then turn off. Vehicle will be enabled to start and run. If a problem exists in PATS, THEFT indicator light will stay on or flash continuously.


NOTE_ The best action is to clear the code, by using a diagnostic CPU. Plug the CPU into your in car port, under the dash. Follow the instruction on the CPU display to clear the code. if the engine dose not start after the code is cleared, this will indicate that there are some issues with the PCM, or PATS

IF YOU REPLACE SENSORS YOU HAVE TO ERASE PCM CODE TO TURN OFF CHECK ENGINE LIGHT.IF YOU DONT IT WILL KEEP LIGHTING UP.

you need to replace the dash cluster, their failure is common at about 10 years of age