What i usually do is take a flame thrower and fire it right up against the block seems to do the trick pretty good.

Anyways to the OP i live in SD so i have a general idea of what your workin with, plug your truck in below 0 degree days, and personally if you want a cheap way to block the air going to your radiator just get some cardboard and cut a piece to stick in front of your radiator. Guy i know just covers the whole front end of his radiator heats up in no time. And i think the airflow from the back of the engine does good enough to keep it from overheating cause he went the whole winter without any problems.

 

I'll be doing the cardboard thing this winter when necessary. I can't see spending much on something I only really need a few days out of the year.

Watch, now that I've said that we will probably have record cold for weeks on end this winter.

 

My source was the Cummins site, however I was too lazy to link the .pdf, it took a lot of searching to find it.