how to figure out what part of my heater needs to be replaced??
 

I just got my 68 running and driving, and i tried the heater for the first time since i've owned it, and after about 10 minutes of driving you can tell there is warm air in the cab, but you can't hear the heater or anything. doesn't sound like it is on at all. If anyone knows how to diagnosis the heater so i know what to check that would be excellent. thanks alot, nate

First step is to run a wire from the battery positive terminal and hook it to the terminal on the blower motor (orange wire on heater box under the hood) and see if the blower kicks on. If it does, you gotta look at your wires and switch, if it doesn't, then go to the parts store and get a new one.
Tech tip, the blower for an A/C truck bolts right on and puts out more air.

sounds good
 

I'll give that a try after the superbowl. Yeah i also heard to get an AC blower whether you have AC or not because it'll blow more air.

that is very true, im plannin on gettin one some time this week and hopefully have it up and runnin on my 70 gmc, im gettin tired of drivein about 30 mins before i get any heat in the cab, but as far as the ac blower is, it will work and will blow alot better then non ac blower