i have an 1988 chevy s10 4.3L 4wd extended cab. it has potential,what should i do with it buildwise?  

should i put air lockers on my truck or automatic lockers.and how big of tires can i go b4 changing the axles,33's?/i heard that autolocking lockers can give out on you when your driving on the highway.  

I wouldn't recommend auto lockers unless you're going to use your rig purely offroad. You're best bet would be an air locker or electric locker that way you can have an open/limited slip on the highway and then lock the axle if/when you need it. For tire size I wouldn't go pass 33's with out some more build up or changing axles. That's just too much weight and stress on the suspension and axles.  

Good advise on the lockers as "automatic" spider gear replacement lockers have no ability at all to power wheels at differing speeds in a turn. It is either both tires same speed in a turn under power with one skidding or outer wheel free wheeling under light power or coasting in a turn. They can also be a heart attack on icy, snowy, slick roads too.