You want as much buzz as you can get right off idle. That's what the factory goes for. The torque converter won't flash if the engine can't hit it hard enough. It's a big mistake to go for a lopey idle without considering the converter and gearing. If it's a manul trans, you have a barnyard gear so it doesn't matter as much.
As to the carb, you want as little of a carb as you can get away with without restricting top-end power. A carburetor that is to big has lower airspeed and doesn't suck fuel as hard through the jets. A small carb fuels the engine better at low rpms, but you don't want it so small that it will restrict airflow at higher rpm loads. If you pull that trailer on the highway, you'll want to make some power. If your engine was 100% efficient than it would need only 500cfm of air to make max power at 5000rpm. A great running 350 could live with a 450cfm. That's what I would shoot for. The reason is that at max power and rpm the throttle plates are standing wide open and the airflow is the smoothest through them as is possible. A Quadrajet has two tiny primaries so it has great low-speed response, but those big secondaries are a crutch so you can use it on anything. Probably the best you can do for that engine in that truck is a 500cfm Edlebrock/AFB. The AFB was my favorite carb.
The intake manifold doesn't matter that much. Whatever you can find that has a square bore and is designed for low-rpm use. A Performer or something similar. You want to keep the port volume small so when you open the throttle there is a smaller amount of air that has to move. A larger plenum manifold like a Torker has more air to accelerate and it takes time for that heavier amount of air to get going.
The cam you want the valves to not be in the way of the airflow, but the duration has to be low so the engine doesn't lose pressure. You want the valves to open and close rapidly and exactly when you want them to. You would like the exhaust leaving to pull a little of the intake charge in behind it. Generally the intake opening point is considered the most important event in valve timing. That means you should make sure that whatever cam you go with is installed exactly as the grinder says on the spec sheet. That's what degreeing a cam is. Anyway, I would go with a hydraulic roller conversion--Competition Cams K12-407-8 should be their smallest retrofit roller. That's pretty expensive. If you want to keep the flat tappet hydraulic than K12-230-2.
Get some cheap, small-tube headers, or run the manifolds. I like manifolds better because they last longer.
And, again, HEI if it doesn't have it.
EDIT:
I forgot to respond to your 6.2 question. An atmosphere is 14.7psi. If you had 14.7psi of boost that was at air temperature your engine would be twice the size (more because 0psi of boost is more than the vacuum throttle-platted gas engines have)--displacement is air. I get 12psi of boost. It's hotter air so it has somewhat less oxygen, but imagine that your engine went from 350cid to 600cid. That's what a turbo does. Do I like it?
Hell yes. The horsepower isn't more than a well setup 350. But it comes in at a much lower rpm since the turbo is pumping air and the pistons don't have to speed up to do it. And the torque is much more. I had a TBI 350 and it did the job but it worked at it. And if you tried to use its 200hp it would suck the 34 gallon tank flat in no time. You could pull up hills at 65mph but the pedal was to the mat and it was downshifted a couple of gears. Much better to have an engine that doesn't have to downshift. Mileage goes way up (the turbo 6.2 gets 16 towing loads that the 350 got 8) and it's more relaxing. Better to spend your money finding a 6.2 and a turbo if you have the patience to wait for a Banks kit to show up on Ebay. I paid $900 for the used kit on my truck. I had a new turbo from another kit I had bought new for another kit. I still have a kit for the newer generation body but it doesn't come close to fitting our trucks. I may use it in my B2.