I just did this on my 70 Challenger. It's not that difficult at all.
You will need to buy the pump motor, 2) cylinders, a set of hyd lines, and a switch setup
of some kind. Wiring is all there except wiring at the switch. That harness can be purchased
from Evans Wiring for $125 or you can make your own. The other big cost is the switch. It can
be bought new repro from PG Classics for $205. You will also have to try to find a 30A circuit
breaker that goes in the fusebox. Now all that being said there are may shortcuts and saving you
can make if your somewhat handy. I couldn't see paying $200 for a switch, so I used a regular switch
from the auto parts store. It has a chrome handle/bat, but that's the only difference. I had to make a bracket
that mounted to the original place with a hole centered to mount the switch. I adapted the harness without
cutting off the original plug with some terms and wire. Taped it up and go. I bought new woodgrain overlays from
performance car graphix for the dash. They have some blems that they sell for the cheap. I couldn't find a flaw i them.
I bought the new harness because I was buying a bunch of other wiring for the underhood area and he gave me a decent discount
because of how much I bought. The circuit breaker I couldn't find, so I used a ATX style breaker and taped the wires
and wire tied it by the fuse box. I can supply a few pictures of some extra parts, but the car is together so it wouldn't be much.
I have another harness for my 71 Convert if you want a pic of that.