I found a 3 speed hidden ratchet shifter out of the 70 camaros.. And I'm wanting to install it into my 84 camaro 700r4 tranny.. How would I go about doing that?

 

So I'm actually just wanting to know how to install a 3 speed shifter in a 4 speed tranny

 

"3 speed" and "4 speed" are likely to be the least of the issues you'll encounter.

This sounds like a brutal backwoods hack job destruction of whatever attractiveness the car has remaining. Assuming that you're not "that kind" of person, it's probably not "A Good Idea".

I would begin with the Patented EEEEEEEZZZZZY 2-Step Method in preparation for all other activity:

Step 1: Sell shifter that WON'T fit your car, to someone who has a car that it WILL fit

Step 2: Use cash obtained in Step 1 to buy shifter that WILL fit your car

Then go from there. The answers to many questions should become much clearer along the way.