Go to this url and you will see a complete right up on how to do the swap.
http://www.pirate4x4.com/forum/showthread.php?t=775780Your engine has to be an 83 or newer engine to do the efi swap. The 79-82 heads do not have the holes to mount the lower intake plenum.
If it is 83 or newer then your going to need a full efi wiring harness, efi tank and fuel lines, complete intake manifold and a lot of time.
To do the wiring swap takes some time since your gonna need to remove a lot of your dash to get the old one out and new one in. If your truck is a 2nd gen then the gauge cluster will work. If its a 1st gen then you need to modify the harness to hook up to the stock cluster.
All in all if your mechanically inclined then you can do it in a few days work.
Just make sure you get a complete wiring harness.
One other option to efi swap is to go propane. Its better then efi and a lot more simple.