Bob N wrote:

We live in a 100 + year old house and just recently pulled the carpet to
find the heartwood pine under it. There were several boards needing
replacing during the refinishing process. Our floor man found that the
yellow pine at Home depot was nearly a perfect match. We have been very
happy with the results.
....

That's pretty remarkable given that new SYP probably came from trees
less than 30 yrs of age. How close a match will probably have to do w/
whether what you previously had was plainsawn or not--the close grain of
old climax forest pine won't show as much in that case.

I'd suspect that there is a noticeable difference in hardness though?