When I put a EFI 6.0L with 4L80E trans in my '70 Impala, I had a company called Speartech reprogram my computer and modify my harness. The owner, called John, is very good and very helpful, you should contact him... His site will tell you more, he will also help with what parts you need from your donor, with A/C,...
http://www.speartech.com/Then, you need to go and take a look at a site called LS1Tech, in the chapter called Conversions and Hybrids (
http://www.ls1tech.com/forums/conversions-hybrids-28/). They put these engines in everything and there is a lot of knowledge available there! Even if no one has put one in a '41 truck, there is a lot of things that will help you there (fuel system, cooling, programming, lots of little things...). I would not have been able to put the 6.0 in my Impala without this site! Just ask your questions, just like here! This is also the site where I heard about Speartech, which is a sponsor of that site, by the way.
