satellite engine in a duster, advice?

I think you're reading to much into this swap. I would not switch out the k frame, just the mounts. Can't tell you about the exhaust manifolds, but I have a set that will work if you need them. The brackets sometimes differ from car to car and especially from truck to car.

But as far as an LA318, they are all the same. Headers, you couldn't find any, they make em everyday for your application. I have a set in mine I got from Summit for 100 bucks, certainly not a top of the line set, but they are functional and fit the budget. I will say this if you are struggling this hard you might want to stick to the manifolds for now, as the headers in an A body can be rather trying to install at times.