I have been stuffing a 6.1 in a 72 Demon. Feel free to PM me and I can tell you about the roadblocks I have encountered. I have a build thread on here as well. It has been a tough go but I think it is a blast and makes for a great ride. There are several on this forum that are exceptionally talented and have done what you are doing. I am more of a back yard get to it when I can vs real builder. Check out some of these guys threads under the Hemi swap tab. They are remarkable.