Dan, I have some '51 style guards. The '51 HJ bumpers are flatter vertically so the guards are not the same as some of the later ones. The early guards were used front and back on the '51 and early '52. The '52 Corsairs have the more vertically rounded, pointed bumper on the front but the back is the same as the '51. The '53 has rounded pointy bumpers on front and back. The guards a different.
I have a bunch for a '51 if that's what you need. Let me know and I'll make you a deal.