I think this may have been covered with GTSdart340's post; staying with your 413 Ray, I think this is your only option:
Big Block to 518 Adapter PackageThe "small block" designation is a bit mis-leading, in a 1500 Ram that transmission is factory rated for around 12,000 pounds. I've gone up to 14,100 on my 46RE and it didn't hurt it. My 46RE failed at 240,000 miles.....I have this and other reasons why I despise this transmission, but, I think it's still suitable for your application.
You would have to contact them to see if a lock-up convertor can be used.
The eight speed though.......wow, if one of you Guys pulled that off on a carbureted small/big block, it would be a big game changer in Hot Rodding Mopars. I have an
idea how to do it and it's kind of simple.
