Well, since you have an '87, you have a couple of ways to go about it. If your truck still has the tbi fuel i jection, you could run a hidden kill switch to the fuel pump. The other option is a kill switch for the starter. Both for double protection.
The fuel pump switch is great. The starter kill not so much since many times on a hot wire, the their is going to use a screwdriver and cross the solenoid anyway depending on their method.
As far other locks and more variables, Don't even sweat that. It is what is, and MOST theives after these trucks use a slide hammer and pop the ignition cylinder out. That's how we repossed them in the 80's. 15 - 30 seconds and it's started up with unlocked steering column and ready to drive.
I'd do the fuel pump switch, and I'd also splice into the positive side of the coil hot wire and put a switch to ground. With the fuel pump switch OFF, the pump won't work, with the ground to + coil switch ON, the coil is grounded and the distributor can't get any spark. Someone else might confirm or deny the safety of that coil switch though. I did it to my older truck running a Mallory Dual Point dizzy, but I'd want to make sure the grounding of the coil can't cook your HEI ignition module. I don't believe the 2 are related at all so you should be fine.
If they are to stolen by tow truck which is common these days, not much you can do about that. The crooks know the steering wheels will lock, so they hook up to the rear wheels and drive off knowing the front wheel will only turn so far before the steering wheel locks and they don't have to rope it off. With that said, You could always turn your wheels half way to the left or right before shutting the truck off so if one was to steal it by tow truck, they'll be dog tracking badly and maybe even bad enough they'll pass and move onto the next one unless they want to Slim Jim it and pop the ignition to straighten the wheels, but most won't take the time.
