Good question... I haven't done it but would imagine the only real difference would be the divorced choke set up to the married one on the newer ones and of course more vacuum line ports and it may have a leaner fuel curve... I'm sure someone with more knowledge on the subject will chime in and let you know...
The 78 carb will be very lean and you will not likely be happy. Go with this rebuilt modifies carb, this one has all the modifications already complete... This one will run great, I have bought a few carbs from Ken, he does them right: http://www.everyday-performance.com...:category=578011&mode=product&product=6010109
Just a note...For my 12 sec 455... I put a ruggles recipe on a 79 350 buick carb and it is the baddest Kick ass carb ever. I have had holly's, thermoquads, carter's, but I love jets. Once the correct recipe is applied, a qjet is what you make it to be. Just my 2 cents.