I dont think that it will be safe for yuou to try and fabricate your own NOS kit. However a NOS kit in a diesel engine would not be of any help as it would lead to immediate detonation.
Rather suggest that you do a search on the web for propane fumigation for diesel's (works best with turbo diesels) this link should be able to get you going on your project:
http://www.mrsharkey.com/lpg.htm
However a note of caution "No welding near the LPG cylinder"