To me there are 3 areas of this. You need wiring, you need the solenoids, and you need to make the solenoid fit. You could piece some of this together with junkyard parts, but maybe you don't want to. The cool thing about it is that you can get solenoids everywhere that'll work.
I just bought myself a lifetime supply, for my own cars, of these:
https://www.surpluscenter.com/Electrical/Relays-Contactors-Solenoids/Electromechanical-Solenoids/12-Volt-DC-Power-Door-Lock-Push-Pull-Solenoid-Black-Widow-PDL-50-BOX-11-3346.axdI don't exactly recommend them, but for the money, I figured I'd get by with these for solenoid replacement only. I am already running one of them in the Redbird, but it had locks originally. Just about anything will fit if you're open to have a screw hole moved over a little. The top link is pretty standardized. I just installed a similar setup into a car without power locks (not a Firebird) and really it seems to be fine. The clamp-on-to-the lock knob is a means of making it fit anything, and you could do better than that. You could make a linkage to the original location. The kit I installed was this:
https://www.a1electric.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=AEOS&Product_Code=W01FI don't like the controller in this kit, and 2nd-gen Firebirds never used one. I just mention it because the solenoids obviously came from another supplier. The same supplier, probably for this:
https://screamingchicken.com/1970-81-camaro-firebird-door-lock-install-kit/Which is direct fit. $119 with the actuators. It's a lot, right, compared to $5.10, but it'll fit.
On the wiring side of it, your car, if manual windows, will be missing the rubber bellows for wiring to the door. If you do have power windows, it'll be there, but it sure is hard to get a wire through it. You can do it. If you don't have the bellows, I'm not sure anybody makes it. You'll find plenty of kits online "for a 1970 Firebird Camaro" but I don't see this bellows. Once you get something to work there, you have to decide if you want a GM power door lock switch on each door (which these are common as an old shoe) or whether you want a pre-1978 single toggle on the dash, or neither. The dash switches are kinda rare. It seems to me that it's popular now to use wireless and just ignore this problem.