Despite what everyone says, you'll find your DSLR lens will work really well on 4X5. There really are only three problems or issues to deal with:

1. No one makes adaptors, but you can easily make one using parts from the inexpensive extension tubes from ebay. Just cut a large enough hole in a lens board and epoxy the lens adaptor end of the extension tubes to the lens board.
2. A Packard shutter can be used in front of the lens, if you can figure out a mount.
3. All of your subjects must be within 6 inches of the lens as it won't focus any further than that and have an image circle that covers 4X5.