When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I would recommend going with a sealer. The basis of the paint is what is underneath it; prep the car, seal it, prime it and then paint.
I just did my 79 in my garage, my car was originally gold then painted red. I did not want to chance any weird interactions between filler, old paint original paint etc. Sealed it up, the primer stuck like crazy to the sealed coating. Seal it! It's the foundation of the paint.
I would suggest a sealer in most cases.....If the paint isnt busted thru and depending on what you are looking for, you might be able to get by without a sealer. If theres just a few spots...you might could use some spot primer.
Don't even think about skipping the sealer, If nothing else it's cheap insurance.
Like stated earlier, it creates a barrier between your final topcoat and the mysteries that lie beneath, and you don't want to find that out down the road.