Nice set of options! Although you could get a similarly configured 326HO together, and the 326HO is a pleasant little engine indeed, I see no reason not to enjoy it with the 400 in it.
If you decide to sell, the car won't be numbers matching anyhow even if you do spend the money replicating a 326HO with all the correct and dated parts. Numbers matching is only until the original engine is gone.
Vikki 1969 Goldenrod Yellow / black 400 convertible numbers matching
