I used a new auto parts store vacuum pot with my old 331 dual point distributor. Don't remember what car it came from but it bolted directly to the distributor on the outside and I recall needing to re shape the pull shaft on the inside. A better solution is to get an electornic distributor from Pick-A-Part off an small block chrysler engine from the 70s or 80s. These drop right into a 331/354 hemi. Only modification needed is to weld a 1/4" extension in the flat tab on the end of the distributor shaft. Just make sure the bushings are tight on the donor distributor and you will be fine.
If your friend wants to go with the stock dual point, have him drop me a note and he can have my old one with the vac pot installed. If he wants to go the electronic route, have him send his email address and I will send a picture tech article I wrote a few years ago on the conversion.