Toggle link guns are notorious for being Over All Length sensitive. My own '73 in 44-40 only likes rounds that are .010 or .020 over the Max length listed in most manuals. Any shorter, and it doesn't like to feed them.
Here's what happens in a toggle link gun like a Henry, '66 or '73. When the magazine spring forces a round out of the tube and onto the cartridge elevator, the only thing holding the next round in the tube is the round already on the carrier. More recent designs have a mechanism that keeps the next round in the tube, but with a toggle link, it is the round on the elevator that is blocking the next round from coming out. The round on the elevator is forced to the rear by the spring pressure of the rounds in the tube. The round on the elevator butts up against the rear wall of the well in the receiver that houses the elevator. So the shorter the round on the elevator is, the more of the next round can poke out of the tube. Some amount of the next round always pokes out, because the round on the elevator must be slightly shorter than the overall length of the elevator, in order for the bullet not to snag on anything as it rises in the elevator to the level of the chamber. So the longer the round on the elevator is, the less the next round will intrude into the elvator area, and the shorter the round on the elevator is, the more will intrude. Are you with me so far?
Now Mr Henry was no dummy, so he incorporated a chamfered face on the front edge of the elevator. The purpose of this chamfer is to sweep that protruding round back into the magazine as the elevator rises past, allowing the elevator to slide by with the round it is raising up to chamber level. But there is only so much space available on the elevator for this chamfer, and so there is a limit to how much a cartridge can protrude out of the tube. Too much poking out and the chamfer does not sweep the round back into the tube, but instead, the carrier simply jams against the offending round. Generally speaking, most carriers can be relied on to sweep a round back in that is protruding about as much as the thickness of a rim, but not too much more. So the length of the round on the elevator governs how well the elevator can slide by the magazine without getting caught.
It is possible to alter that chamfer so that it can sweep back a round intruding too far. But there is only so much material available to alter. If the round protrudes too far, the chamfer simply cannot be altered to accomodate it.
Instead, Over All Length of the cartridge has to be set at an amount that will keep the round in the tube from poking out too much.
Uberti rifles have varied over the years in these critical dimensions. Sad but true. As I said earlier, a 44-40 1.592 long, the book Max, will tend to jam up my '73. But if I seat the bullet out so that the round is 1.602, or even slightly more, the gun works like greased lightning. I have altered that chamfer as much as I possibly can, now it's all up to OAL. My gun is an old one, made in the 1980s, and it is a little bit unusual in this regard.
I'm not familiar enough with the 44 Colt round to give you a definitive answer, but it sounds like the round teeters on the hairy edge of uncertainty regarding reliably feeding through a toggle link. It is entirely possible that by loading them long enough, you might get them to feed reliably without any alteration of the gun. You will want to be sure you use a bullet that allows crimping in the crimp groove however, since lacking a strong crimp the bullets may get forced back into the cases by the strength of the magazine spring. I found this problem when I started loading some extra long dummy 44-40 rounds for my '73, but with them stuffed full of Black Powder the bullet has no place to slide back when I run live rounds through it.
Since it sounds like you already own the Open Tops, would it really be so terrible if you shot the 44 Colts in them and shot the rifle with the 44 Sp rounds it was chambered for? I've been shooting 2 different calibers in CAS since day one and if I can keep things straight, anybody can. You may find that you can shoot th 44 Colt rounds, you may find that you need to stick with the Specials. Just how much is the difference between the recommended Max OAL of the 44 Colt rounds and the Max OAL of the Special rounds, anyway? Like Capt Augustus said, some 45 Colt toggle links will feed 45 Schofields, some will not. They're not quite all the same.