HOW-TO convert your oil pressure gauge by Michael Maroschak

1. Remove sender unit's wire.
2. Remove oil pressure sender unit with a 1 1/16" socket or the special oil pressure sender socket (which actually works better if you have one).
3. You might have to move some of the accessory belts out of your way.
4. Put Teflon tape on the new sender unit's threads.
5. You may have to use a 7/8" open ended wrench to cock the threaded pipe (that comes out of engine block) slightly one way or the other.
6. Thread in the new sender as tightly as you can with your bare hands (as you would your oil filter). It's easier if you make sure the sender and your hands are dry and grease free.
7. Re-connect sender unit's wire.
7b.  A small number of Thunderbirds have the 20 ohm resistor located on the oil sender wire approximately 5 inches form the sender itself.  If this is the case, bypass or remove this resistor and skip steps 8 through 14 (inclusive).
8. Remove trim around instrument cluster. There are 2 screw at the top, then ease it on out.
9. Remove screws around instrument cluster. Ease it out several inches, tilt the bottom out, and gently pull the 2 connectors off.
10. Be careful not to scratch the instrument cluster's bezel.
11. Flip it up side down and solder a piece of 18 gauge (insulated) wire in parallel to the 20 ohm resistor behind the oil pressure gauge. There is no need to remove     the resistor. Be careful not to melt the plastic.
12. This would be a good time to remove the bezel and clean it.
13. Also a good time to replace any burnt out bulbs.
14. Replace instrument cluster.
15. Start 'er up & check it out!
16. Remember to check for leaks.
17. When cold: between M and top line When hot at speed: M When hot in gear idle: between N and O When hot in park: O
18. The oil sender part numbers are as follows: Standard Motor Products: PS-60 Echlin: OP6091 Motorcraft: SW-1547-B, E4ZZ-9278-A