I'd put it at 0 if you want more power towing get a cam and degree it according to the spec card. Shouldn't need lifters as your engine should have roller lifters and new intake gaskets might already be needed anyway.
the truck V8's didn't get roller cams until the 96 model year- but some blocks have all the provisions for the roller cam stuff.. one easy way to gain a ton of power and torque in the throttle body trucks is to swap in a newer vortec long block with the GM TBI intake manifold.
i'd install the chain straight up.. then once it's running i'd pull the ignition timing ahead to about 10 BTDC- make sure you find and unhook the tan wire that goes from the distributor to the ecm, or it will compensate on the fly and put the timing back where it started. just doing this will make the truck noticeably more powerful and gain some fuel economy.
throttle body spacers are known to wake these engines up, as well as the spacer that brings the injectors up out of the throttle body.. get rid of the spacer between the throttle body and air cleaner to let the air get into it better, and throw away the big baffle in the air cleaner duct between the fender and air cleaner housing- make a new duct out of cheap clothes dryer ducting to get the cool air into the air cleaner. if it has a single stud holding the air cleaner on, you could get a lid off an older truck (80's) that had the taller element and be able to use the stock stud as well as getting a bigger air filter. if you have the dual studs, you should be able to find a single stud setup on a different truck in a junkyard, which is something you'll have to do if you put the spacer under the throttle body, anyways, since the dual stud air cleaner lids are mounted with studs built into the throttle body bolts.
if you don't have emissions to worry about, get rid of the catalytic converter and put a free flowing muffler in it.
on top of all this, make sure the cap, rotor, and plug wires are good and put new plugs in it if it's been a while or you don't know when they were last changed. maybe throw a fuel filter in it while you are working on it.