Here's a start:
1. Pull the engine out of the truck
2. Bolt it to an engine stand
3. Pull the valve covers
4. Pull the cylinder heads off
Now while that's done, drop the fuel tank and drain it. Inspect and replace all fuel lines as is necessary.
If you would like a perfect running engine by all means pull it and do a rebuild. If you would like to see if you can get it to run and not worried as long as it doesn't stink up the neighborhood with smoke and fumes then pull the plugs and pore in some penetrating oil use a big strap wrench around the lower pulley and try to pull it back and forth a little at a time until you are able to turn it all the way around. Don't be in a hurry take your time and don't try to push to hard in one direction or the other. Caution do not use a socket on the crank bolt, it will break off and then where will you be. You may want to pull the starter motor and use a heavy screw driver to turn the flywheel, may be easier. My skid steer was left out for about the same length of time and it worked for me, it's been over fifteen years now and it runs great.
Yeah....an engine that old, you need to tear it down to the short block then see if it is worth rebuilding.
remove the spark plugs and fill the cylinders up with diesel fuel. and leave for 24hrs..
tear it apart and see if it is even worth rebuilding.
It has sat for at least 9 years
