Jim Church dug up this info on N6172C:

" N6172C is, s/n 44-73454, c/n 122-39913, and was registered as such between 1963-1967. It went through many owners before winding up in the hands of Richard A. Bjelland, who flies it in a 352nd FG "blue nosed bastards of Bodney" scheme as "This-Is-It!" This was the mount of group commander Col. Joe Mason. It is currently registered N2051D. It was rebuilt following a crash by Cavalier Aircraft Corporation in 1968 as a "Cavalier 2000." Gordon Plaskett rebuilt it to stock condition after another mishap in 1973. "

Thanks Jim you got it.
Other owners of this P-51 include Rufus Applegarth, John Schafhausen, and Richard Bach. Bach was owner during the '73 accident.