I've never done this, but I know someone who has.
Here's what I remember about his project:
Stock cam need not be replaced... works great. as is.
Might want to replace the valve springs with some a little stronger (but, not much.) Stock 340 springs waould probably work well.
Many people have welded the turbo mounting flange to the stock, cast iron manifold, successfully.
My friend used a junk-yard Buick G/N turbo.... cheap.
He used an unknown 2bbl carb on a Super Six manifold with no intercooler at all, and no water/meth injection.
Stock ignition was more than adequate. 18 degrees of total spark advance (initial plus mechanical advance) Yes, 18 (no typo).
The carb will need to be modified for blow-thru usage.
A drain-back hose will deliver oil from the turbo to the oil pan.
Colder spark plugs (withhout an extended tip) will be desirable.
Some sort of an air cleaner will be necessary.
A pickup truck has a lot more room under the hood than a car; space for this stuff should not be a problem.
Might be a good idea to run premium fuel.
My friend did this to a '70 Dart Swinger and the result was a time slip from the drag strip that read 102mph, and a 12.95 e.t.
Your truck might not be quite that fast, but 340 Dusters (stock ones, at least) shouldn't be any problem for your newly-invigotated pickup.
It will be "peppy," for sure....
Bill