[Zoomad75]

Do you have a/c or not? It's really easy if you don't have a/c. Two nuts on the fire wall side (they are the stamped speed nuts on long studs, cant miss them), One bolt from under the dash on the far outboard side. You can see the bolt if you take your glove box door out. One more little screw holding the box to the defroster outlets (right in the center above the tranny hump). Disconnect the cables and the complete heater box comes out from under the dash.

Once you have the box out there is just one screw holding a wire bail that retains the core in the box. Clean up the mess as it's probably all wet in there and then reverse the order from dis-assembly.

The non a/c trucks are a breeze. I can do mine in less than a half hour now (but I had recent practice too!)

A/C trucks take a little more effort. I havent done one of those on this style of truck.