i went with the 545....tunnel mods were hard but not impossible for a shade tree welder to do,,,,,,I actually cut part of a tunnel out of a 1965 pontiac tempist I had left over as a parts car on a GTO restoration..it worked good
I am currently swapping a 6.1 hemi into my 70 Challenger convertible. I just bought the domain name ebodyhemiswap.com..... I will be opening it soon. It will contain all the information about my swap. I hope to have a forum on it so others can share....keep checking ebodyhemiswap.com....