The story of Ozark Mountains Arms is rather convoluted.
The company was originally founded by Milt Hudson as the Mountain Arms Inc. in Ozark, MO around 1977. In 1979 Hudson brought in a couple of partners who very quickly crowded him out of the company.
Milt Hudson formed a new company called The Hawken Armory in 1979 still based in Ozark, MO.
His former partners renamed the original company Ozark Mountain Arms in 1979 and moved it to Branson, MO. They continued to produce the same rifle that Milt Hudson had.
At the end of 1983, Gene Arnaud sold Ozark Mountain Arms to Bob McKellar and the business was moved to Ashdown, AR. Ozark Mountain Arms continued to operate in Ashdown, AR until at least 1987.
In the meantime, Milt Hudson plugged away at The Hawken Armory making its version of the same Hawken rifle as well as a squirrel rifle. The company apparently changed owners and moved to Hot Springs, AR in late 1980 or 81. I don't know how long The Hawken Armory operated after moving to Arkansas.
Milt Hudson's Mountain Arms Inc. Hawken was a copy of a contemporary Hawken that was made by Ed White. Ed White had made his rifle as a copy of an original in Art Ressel's collection. This was the same original Hawken that Art made most of his molds from for his Hawken Shop Hawken. There are some similarities between the Mountain Arms/Ozark Mountain Arms Hawken and the Hawken Shop Hawken, but also major differences. The Ozark Mountain Arms rifle used commercially available parts except for the breech plug and the hammer which is similar but slightly smaller than the Hawken Shop hammer. The Ozark Mountain Arms rifle used a 1" straight octagon barrel where the Hawken Shop used an 1⅛” tapered barrel. The Hawken Shop also used proprietary 1⅛” breech plug, butt plate, trigger guard, triggers, and nose cap.
The May-June 1980 issue of Muzzleloader had a review of the Ozark Mountain Arms Hawken. The article described the barrel as a Green Mountain product that was 1" across the flats, 33¼" long, and available in .50, .52, .54. and .58 calibers. It was made with a Ron Long lock and L&R triggers. Another review in the October 1982 issue of The Buckskin Report described the same components but listed the barrel length as 33¾" long.
Prior to the change in ownership and the company move to Arkansas, they apparently changed to using an L&R lock. Another product review in the July-August 1983 issue of Muzzleloader listed the components as Green Mountain barrel, L&R lock, and L&R triggers and stock shaped by Reinhart Fajen.
Looking at my two rifles, a Mountain Arms Inc. and a Ozark Mountain Arms, the breech plug appears to be a proprietary breech like the hammer. It is a slant breech similar to Track's PLUG-RL-16-3 or PLUG-LR-16-3. The butt plate is the same that GRRW used on their early Hawken rifles with 1" barrels and similar to Track's BP-HAWK-L-I. The trigger guard is same as Track's TG-HAWK-L-I. The proper L&R triggers are the ones with the straight front trigger.
This should get you started on sourcing parts.