Single or Twin turbo setup for 360?

Towing with boost can be absolutely awesome or go horribly wrong very quickly. Lots of load makes lots of heat and extended periods of boost in high load situations at LOW rpm means your tune has to be perfect and component selection/sizing has to be carefully thought out. A focus must be made on a very efficient intercooling system and engine cooling system. Turbo sizing is critical, you want to size the turbo such that you are not always in boost at light load, but also not so large that you have to spin the engine up hard to make any boost. This takes lots of math and lots of studying compressor maps. I would recommend reading as many books as you can get your hands on, I always recommend “supercharged” by Corky Bell, it has an incredible amount of good boost theory in it and the info applies to all forced induction set ups. Honestly for a small block in a towing situation in a heavy truck your money might be better spent on cubic inches. I think a Stroker at 408 cubes might serve you better as a starting point.