As long as you start with a car that has some resale value (and not like me who has a practically unsellable car that handles awesome
).. its really down to what you like the best.... the nova will be more expensive to build as you will be discarding the whole suspension and subframe... whereas the chevelle can be built to handle extremely well on the oem chassis with bolt on parts only... as long as you box it and run solid or poly mounts....
A 66 nova would be my choice, try and get a hold of a semi completed project.. it will be the least expensive way to get your hands on one, and they usually come rust free and with a myriad of goodies ...