If you are going to rebuild the 2.8, then go 3.4.
Your 82 was a carb engine from the factory, although you can go with fuel injection, it will be a considerable amount of work, and a donor vehicle with injection will almost be required.
Remember, not only do you need the engine management system (ECU, wiring harness, all sensors etc) but you will also need to set up the fuel system for the injection. The 82 does not have a compatible fuel system for injection.
All of this means nothing if you have the patience, ways and means to do this kind of a project. It sounds like you are going into this big time.
BTW, there are several hidden costs at the web site you tagged. They will probably hit you with a penalty for a 2.8 core, and there is shipping both ways for the engine. If you shop, you can find a good used 3.4 for a reasonable price.
The 3.4 is a drop in to replace the 2.8. Most of the 2.8 components will interchange with the 3.4... BUT... there are a few things you will have to consider.
The 3.4 is balanced differently than your 2.8, so you will need a flex plate/flywheel from an 88 or newer 2.8.
The water pump is different on the 3.4 also. You will need a later serpentine belt assembly from an 86 or newer 2.8, or swap all of your 2.8 stuff (including timing cover) to the 3.4. The water pumps rotate in opposite directions from the 82 2.8 to the 3.4.
Even though the oil pans look the same, use the one from your truck. The crate engine pan may work, but I am not sure.
Headers, intake, distributor, cams and the majority of the rest of the engine components interchange.
If you actually get around to doing this swap, the guys on the forum will be happy to help out with info.
I can say this much: I learned the hard way.
You may have seen my rig... the "Voodoo" truck. It has a ' 3.4 that is set up with every conceivable bolt on or bolt in, short of the rotating assembly. It runs high 14s at the 1320 and is a blast to drive. It also has all of the options like A/C, power steering, brakes and yes, cruise control...