I purchased a home built in 1953. It has two prong and improperly installed three-prong outlets. I have a recessed vacuum to install and the directions require an electrical grounding conductor. My questions is: if I install an electrical grounding conductor along with a GFI at an outlet at the start of a load path would that represent a safe and proper Three-Prong replacement of a two prong system?

Let's not get confused with terminology...
You are installing a recessed vacuum? Does it require it's own branch circuit?
I'll assume it will...if you install a new branch circuit from your electrical panel for this vacuum then you will be able to meet all the manufacturers installation requirements without trying to be "creative"....
By the way, if your electrical service is also dated 1953, maybe you should update.