Dallas,
Sounds like you need a copy of "Gunsmithing Guns of the Old West", by David Chicoine. He has a section on the '73 and worn out links.
You can do a visual inspection if you pull the side plate and put the bolt in battery, lever up. With the bolt closed, the links will be straight, 2 piece, but straight. They work kind of like the folding thing on a folding table, except one part is round, concave, and the other is round, convex.
Straightened out, and pushing on the bolt, they are like putting 2 bricks under a load, total support. They should push the bolt to a snug fit at the breech face, .006 to .008 headspace on the cartridge head.
If you open your gun and work the action, you will probably find badly worn pins and link section ends. There should be no slop with the bolt closed.
If you like give me an address, I will scan and send some pics and some pertinent text.
I found my copy on line, 8 bucks or so, plus shipping, mebbe 12 total. Excellent source of info.
Should you find it is the links that are worn, and not the pins, rare, I think, they can be bought from Numrich Gun Parts, West Hurley NY. I think they are
www.gunparts.com
Cheers,
George.
Edit,
What caliber is it, BTW? And, you would NOT believe the parts value of that original. Last weekend show, one vendor was selling links that looked as though the were buried 20 years and wiped off, 85 bucks eack, steel butt plate 135, etc.