I'm doing the same thing to my '96. I found everything I needed in the way of bolts and a starter spacer, crossmember, etc. , even a block adapter which I'm not sure I need, from a seller who goes by redlinear on ebay.
He is constantly parting trucks and Diesel Dodges in particular. When he dismantles a Cummins/NV5600 for example, he puts the entire bolt set from the block adapter,flywheel, bellhousing, pressure plate, and transmission together on auction. That's alot of bolts! And they're the right bolts. It took me a long time waiting for a 2nd auction to come up on the ones I needed (I lost the first) after I started looking, but I finally got them all for $34 shipped. He's a good honest seller to deal with, and I've gotten many parts from him.
Your other option would be the Cummins Parts counter. I would try there before going to my local dodge dealer(for anything!). Many are flanged-head bolts and you want the right ones. You don't want hardware store bolts holding your expensive engine and transmission together.
If you find a post by CumminsPower98 here on TDR, you will be able to link to his excellent webpages covering his mods. He gives great step by step photos and lists parts numbers for almost everything he comes up with. Included in the NV5600 conversion info is the Cummins part numbers for the starter spacer and the new longer bolts it requires. You only need the spacer and longer starter bolts if you are using the larger NV5600 flywheel instead of a modified NV4500 flywheel.
Wait, here's a link there from my "favorites" file:
My Ram
You can spend a great deal of time there checking out all of his very well-done and clever mods. It's really amazing.
Good luck!