As far as what to watch out for, There have been some issues with the #53 block. I would stay away from the 94-95 years, they had several startup issues, new models always do. There is the issue of the KDP, it applies to all the 12V's, look for leaks in the front timing cover. And if you buy one make sure you take care of it pronto, before any gages. The fix is easy, it took me less then 45 minuets to do and I'm slow. I would buy a vacuum gage and take it with me when I test drive anything, just plug it into the connector on the drivers side firewall, it will tell you the condition of the pump, and HVAC controls. Look under the truck for not only leaks, but signs of abuse, rock damage,excessive mud, etc. If it's a automatic, assume it needs a rebuild, especially it the previous owner towed with it. Pull the transmission dip stick and smell the fluid, it should not smell burned and should be bright red. Check to make sure the CAD or central axle disconnect system is working right, also check the transfer case and it's operation. Look the suspension over, are the shocks leaking? Is there oil on the differential housing, both in the center and at the ends? Look under the carpet, is it wet? Pull the radiator cap and check , is it bright green? any oil? Look at the AFC housing, have the 4 screws been removed or tapered with? feel the throttle cable, is it frayed? they have a problem with that. Do all the dash warning lights lite ? anything stay on? Get a car fax report.