I have a tip for replacing the heater core in a 88-94 model 1500 trucks on the passenger side the box the heater core is housed in can be dropped andthe core is right there. Unscrew the clip that hold in the core and take it out. take off hoses of course.and Put the new 1 in. There is 7 or so screws the ones in the back are kind of hard to get to you have to feel for them. Use a quarter inch socket with long extentions. It took me about a hour and a half to complete mine. Hope this helps someone.