Can't speak for all the hemi hardtops but the one raced by Gary Ostrich here in Iowa was originally purchased by a man wanting a max wedge. Ordered a max wedge 64 Plymouth in January and was informed production stopped but could get a hemi later.

When the hemi arrived in June/July he didn't want it and Gary ended up with it. This is the car now owned by Pat Goff in MN.

As for the Nichels Engineering cars I've seen paperwork on some of the race cars with the vins listed and they do not match any of the hardtop hemi cars.

As previously stated the stock cars were primarily built in early 64 and the hemi hardtops were built in the summer.

FYI,
Alex