the 6.5td has issues that may be in 1k-2k range to fix I agree a 350 is fast easy and a butt load of parts and performance options. Simply asking a 350 to be a big puller is maxing it out.
I know you can make it work gearing bolt on stuff but for torque I like displacement. 454 big block etc. My buddy wants me to go with a newer 6.0 5.3 or 8.1 Maybe I am just stuck in the dark ages I like carbs ( not an expert mind you just like em).
Options and opinions are varied on this subject and I think we all gain from these discussions.