There aren't shops that specifically specialize in Dakotas. Few even specialize in Mopars. Just look for a shop with a better than good reputation especially with performance builds. Then expect to be told that your 3.9 is almost a lost cause because there isn't very much in the way of performance parts. If you want it to be a toy you an show off, consider an engine swap (please don't stick an LS in it. Chevy's suck!) Mopar has a ton of engine options, some being more exotic than others with only your wallet being your limiting factor.
There is a mechanic who is doing a beyond serious build on a 3.9 & posting his progress in the 3.9 subforum of the engine section. You might be interested in following that, as at this point it appears as if he is near completion, & since he has posted everything else that has happened with that engine, I expect that he will post his performance results.
I am kind of thinking you are not going to want to take it as far as he has.