Man...you guys just sent me down Memory Lane! Trop...we went with a totally new system because we didn't know how/if our 35 year old equipment worked and if we were going to go through all the hassle--we were going to go with new stuff. We did have many a night just staring and scratching our heads, but we figured it out. Vintage doesn't have an e-body kit that will just plug in, so you have to use their "universal" kit. You don't need the e-body ducts as they were too big for the tubing. We fabbed our own ducts out of thin sheet metal. It's really not that bad of a job...now that we've done it.
Let us know what you decide and we can help you with any questions you might have. Good luck!