A couple of things.....
0. Before you do anything else go to
www.arengineering.com and buy AndyF's book, read it twice.
1. Unlike chevies, Chrysler Corp used the same block across most power levels (except for some oddities like the 340 AAR blocks). So any block is as good or bad as the next. Before you do any machine work on a block have it sonic checked because casting quality is all over the map. It may be that you have to sleeve a hole in an otherwise great block. Do it.
2. I'd start the search for bigblock stroker kits at
www.440Source.com. You should be looking at, minimum, a 4340 crank, lightweight forged pistons and new 4340 connecting rods with 7/16" fasteners.
3. Now after you look at 440Source, there are other places. Make sure that MOPARs are their primary business. There are wrinkles in MOPAR design that can trip you up.
4. Read this site every day.
Good Luck!
R.