It can be done later easily, so big deal there.
I used brass fittings and compression unions to plumb off the governor port and ran a steel cooler line up the back of the motor to a T then the two pressure switches attached to that and a bracket to bolt it to the back of the intake.
The stuff you see online for doing this is not speed adjustable and mounts down on the trans.
Since my switches are adjustable I wanted to access them from under the hood instead of under the car.
The two switches are actually made for nitrous systems and are called Fuel Pressure Safety Switches.
They are 30-70lb adjustable normally open 1/8 NPT electric switches From Jegs online.
Road speed relates real close to governor port pressure, so at 50mph your governor is putting about 50psi out on the governor port.
30-70lb relates to 30-70mph adjustable when used for this, so if you adjust the switch to 50lbs it will kick on your OD at 50mph.
They are for deactivating the nitrous if there isn't sufficient fuel pump pressure.
The way I used them was for when the trans governor pressure reached a certain pressure they would activate turning on the OD solenoid and LU solenoid, but at different pressures. (I set them so one switch activates at 55 and the other at 65)
I started with both switches turned as high as they would go so it didn't accidentally do something stupid like activating lockup in second or something. :D
Then I took it out and drove it, backing down on the switch that controlled OD first until it started shifting into OD at the speed I wanted. (55)
Then I did the same with the lockup switch until it was coming on at the speed I wanted.(65)
Now one more small complication.:D
I used part GM part number A74439A (6lb-22lb adjustable vacuum switch)
This interrupts the power to the lockup and/or OD when the engine vacuum gets lower from acceleration and kicks it out until manifold vacuum comes back up again. (like for passing or heavy throttle)
It is just a vacuum controlled kickdown if you will.
The switches inside the car just interrupt the ground for the two 12v solenoids that control the power to activate OD and lockup.
Let me know if you need more info or help with it.
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