Pictures would be most helpful.
Not running in 4 years means that the motor and or carb might need some work. It all depends on how well it was put into storage.
Going to a V-8 would be a good amount of work. It depends on what v-8 you want to put in there. Ultimatly, you would have to replace the drive as well to match up with the power that the new motor would produce. We know quite well that over powering the gear set in the drive does not turn out well.
There have been a few v-8 cv-16's on the market this year. it would be easier to buy one of them outright rather than tring to retrofit a standard CV-16SS.
Personally, I bought one in rough shape (good floor and stringers, but bad metalflake and interior) for 2K. Motor was good, but I ended up putting over 2K into the interior and other parts. I had 4K into it total, and it wasn't as nice as Jason's who bought his in great shape for roughly the same price.
Sometimes it is easier to buy the completed project rather than trying to restore. Restoration takes a good amount of $ and a huge amount of time.
Pictures, pictures, pictures!