I do understand it would be nice to get an original. Have you called Colaws up in Springfield, MO? It's an RV salvage yard. Who knows what they might have?? How about any heavy truck slavage yard that might have that engine & dip stick??
If you have the original you'll know the correct length. Another option would be to get what you can get and extend it so it will work. Any decent metal shop can rivet, braze, or weld on an extension.
I'd drill two tiny holes about an1/8' or so through the end of the stock or what ever you can find dip stick. Go to Hobby Loby or a good hardware store that sells tiny brass or SS nuts and bolts. Drill holes to place two tiny bolts and once the nuts are on pene the nut with a sharp pointed punch to stop the nuts from coming loose.
There's always more than one way to skin a cat!!!
TeJay Auto Instructor/4-yrs USAF/ Liz: RN/ WBGO 2014 Vista 30T/ F-53/CHF/5-Star/Koni * Bella & Izzy * Golden /Cocker mix/ Louie The Cat* All Retired