motordog80,
They were going to come out with a .45 NEF Huntsman in 2003, but they never released it. I heard it was because of the twist 1-20. Although that twist is too fast for the lighter saboted bullets that everyone seems to want to shoot, it is the perfect twist for a .451" 460 grain slip fit conical. My White M-98 .451 has a 1-20 twist and it's just right for them conicals.
H&R did make a H&R Huntsman .45 cal back in the 70's, but IIRC the twist is around 1-56 or 1-58. Some here have them, they may be able to tell you the particulars.
Here is my loading guide from the 2003 Huntsman OM, notice the .45 caliber (never released) info on top.