Hey, if you don't wanna go through the hassle of modifying the plenum like I did, just get one from a junkyard truck that had the high output heater. You will get some good practise on plenum removal when you do it!
To modify my plenum, I split it open on the seam, drilling out the rivets to do so. I then removed the heater core support piece and made a new one, riveting it in place lower down in the box after measuring the height difference on the core. You should make sure you have this support for the core, because you don't want it to be able to move around. Otherwise, a standard core should work just fine for you. I just happened to have spare time on my hands! lol
Even with the standard core, you should get some awesome heat in the cab.Just so you know, when I tried to track down my heat problem, I also replaced the water pump (since it started leaking through the overflow hole), and also the radiator. The core was done first, and I had lots of heat, but a few months later the engine ran too warm, and that is why I replaced the rad. It was too corroded. I hope the core works for you! I waited about 8 years before I figured it out! Everyone else said it wasn't the culprit, but I just didn't listen, and I am happy with my decision!
Mark


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Ford started it; Ford will finish it!