It depends on if you want a full push button (no key) or to turn your key to 'RUN' then push a button, which in my opinion is pointless. If you want true push button start, there's more to it than that. I had my '91 set up for push button start, and did it like this:
1) You need a 'ignition' switch that puts power on the essentials when you turn the key to RUN.
2) You need an accessory switch that turns on the extras when the key is on run (radio, power windows, wipers, etc). Items 1 and 2 could be on the same switch, but you'll need a big wire. It takes a lot of current to run two windows at a time and stuff like that.
3) You need your momentary on pushbutton connected to the wire that gets power when you turn the key to start.
4) You have to disable your steering wheel and gear shift locks (if its an automatic). For my first gen, you can pull the lock cylinder, rotate the gear in the bottom forward by one tooth, and put the cylinder back in. This makes the 'lock' position on the key slightly forward of the original lock, which lets the wheel turn and lets you take it out of park, without having any accessories running (this took some time and trial and error). This also lets you still drive it like normal with a key if you ever need to, and if you turn it back to what used to be 'accessory' it is actually the steering lock and makes a nice safety feature.
5) you need a heavy gauge power wire feeding all of this with an automatic resetting circuit breaker. I was driving along one day, went to put up both my windows at the same time and it fried the fuse and the truck died...
So...after all that, to start the truck, you flip your 'ignition' and 'accessory' switches, then push the starter button, and away you go.
I used a moroso switch panel from JEGS with extras for lights and all.
Hope this helps you out.