[Will]

I don't see how those two statements are exclusive or contradictory to each other at all....????

A smooth, quiet engine with super torque output would be a great daily driver engine as well as towing engine.

Any controversy in this thread comes from the typical "cubic inches are king" mindset. Which, in reality, can't be argued but shouldn't really be a factor. The question was not whether a 350 or some larger engine should be run but how best to set up a 350 for the desired goals. Whether the 350 is the best possible choice isn't the issue.

I'd think a 350 should work good if you can overcome the compression ratio and valve size issues. How much lift can you run with big valve heads before valve-block interference becomes a problem? If you can get up to .450" or greater lift then it's a non-issue and I'd run the 670s on it. If you're limited to less than .450" then I'd try to find a set of small valve heads that will give a good CR and do some port work on them.

I'd also try to maximize torque in the lower-mid RPMs, say from 2500-5000 RPM. I bet with the right cam, exhaust, and head choice you could get 400 ft-lbs. Work it like a diesel engine - shoot for a narrow powerband that makes as much torque as possible then gear the vehicle to take advantage of that. A little lope at idle would be okay as long as it's pulling enough vacuum.

I bet that Comp HE260 would be a good choice.