B.V.H., just for the sake of discussion only...
The answer to your question has been addressed by Trap, "Good question, I will have to get back to you." jt
Since no organizational rules were addressed in his initial invitational post it cannot be assumed that a H&R can or cannot be used, NCOWS was not listed as a sponsoring and organizing entity in Trap's first post so any comments about NCOWS rules or regs are technically detrimental to any positive discussion here.
To address your logic of the H&R design, I'm certainly no expert but have read many other posts discussing this same concept/logic here and on other forums down through the past few years when the H&R was looked at as an inexpensive alternative to a Big Bore rifle. 'Yes' it is similar in design to the Wufferlein rifle that had a top-break/tip-up style and a lever to facilitate the opening of the breech for loading. That design was and still is a viable style. H&R, now NEF if I recall correctly, has built that rifle in a few models, the most recent has been the one many think is a copy of the original Wufferlein, alas it is not if you look at pics. However, it is close enough to make many think it will pass muster on the Firing Line at some orgs events. SASS does allow it in some classes, NCOWS does not due to the modern redesigning and ejector. Some have said if the ejector is disabled it will be allowed, ultimately it is up to the NCOWS Judge to make that decision then have it approved or not. Again, please refer back to Trap's initial invite post and you do not see that NCOWS rules must be adhered to, this may be case but nothing there indicates so as of yet.
So, 'if' the event is NOT run under NCOWS rules, etc., then your H&R may potentially be allowed and as Trap stated he would "...get back to you.", and I know he will, he is a good man.
You stated that NCOWS "...seem to be splitting hairs that don't need split(t)ing." That is a part of the orgs concept, if you would like to change that then simply establish membership and let any Officer, Senator or Posse Rep. know how you feel on any given issue.
You recently posted on the GAF forum about the Grand Muster, the GAF as a historical group based on the Military would certainly never allow an H&R to be used in the Main Battle Rifle class, so therefore it seems equally the same with NCOWS if you think about it in that form of concept and logic.
Again, just for the sake of discussion, you also mentioned that "...unless someone has close to $1000 of more laying around the H&R is the only .45-70 alot of poaple can afford." If you have kept up on this forum you'll have read many posts about a Big Bore rifle put out by IAB for a lot less than other rifles, it has been fondly called 'a cheap Sharps' and those that have them seem to enjoy them and paid less than $1,000 for them.
It really all boils down to what you want out of a Big Bore rifle, if you only want to shoot one at targets or hunt with every so often shooting under 1,000 or so rounds per year and not for historical events, then the H&R is the best for the dollar, I have one I got used and it is a tack driver with ladder sights and a Lyman 17A front sight. If you want a Rolling Block then hit the gun shows and you'll be able to pick up an older Navy Arms Roller for under $600, m/l and it'll provide you with period-correct design and solid performance. If you want a Sharps-style and will only shoot in the 1,000 round per year arena then IAB can be had in the range of $500-700 used to more new. Older IAB's had some problems but the newer models are said to be better. If you want a Pedersoli a used one can be had for $800 and up depending on sights, etc. A new Pedersoli is in the range of $1,200 and up due to the large increases in import dollars and a reluctance in dealers to order according to Dick Trenk, the Pedersoli Rep. when asked about new rifles on another forum. An American hand-made Shiloh or C. Sharps rifle will run you anywhere from $1,000 up used depending on style, sights, etc., to whatever you want on it as they are generally all custom made per order. Check this and other forums such as
www.BPCR.net and www,.shilohrifle.com to see what is available on their FOR SALE or comment threads as you may just lock-in on a great buy. Checking local papers for auctions is also a good way to get older rifles that have been in a closet, and don't negate that simple two line ad in your local Shopper..."Buying old guns for CASH. XXX-XXXX", you'll be amazed what is out there that oldsters may want to sell but don't want to mess with a trip to town.
You have mentioned on the GAF forum you are looking for costuming, unless you make it yourself, buying period-correct clothing can be as costly as a new period-correct firearm, but as O.T. Buchanan has established in his '3 Levels of Authenticity', which can be seen on the NCOWS website (simply click on the NCOWS logo on the forum then follow the link), start where you can and work your way up, go with what you have and add as you can, hit auctions, gun shows and Trade Fairs and you'll be surprised what is out there. If you can make it to the NCOWS Convention & Trade Fair next March in Kansas City you'll get a chance to see and buy whatever level of rifle and costuming you desire, vendors and individuals will have tables loaded with most everything you'll need.
Now, the fun part of this discussion, if you don't have a rifle that Trap says will work, simply ask someone else going to use theirs and then work a trade for ammo, etc., you'll make a friend and shooting buddy, heck, I'll bet even Del would let you use one of his if he ain't going and all you'd have to trade is a bucket of lard, HAH! If I was going I'd certainly let you use anything I have. We have all been in the same boat at one time or another, the wrong gun, hat, boots, etc., at the right Shoot, not to worry, it'll all work out.
Best regards and never think that there is only one way to get 'r done, just ask!
'Ol Gabe