Howdy Hard Luck,
I can only speak for the Cimarrons but expect the story should be the same for the Taylors.
First, I don't think you can put the '60 cylinder on the '51 frame because of the rebated cylinder (larger diameter in the front). The '60 frame has a step in it to allow the '60 cylinder to fit.
If you are going to want to be able to swap cylinders and barrels to get different calibers, the '60 Richards-Mason may be the most versatile, since cylinders and barrels are made from .38 Spcl to .45LC for this gun using the same frame. Actually the 38 Spcl chambering was originally a mistake by Uberti, so I don't know if they are going to continue making that caliber or not.
The '72 Opentop is almost as versatile, but the 45LC version has different dimensions. The cylinder pin is a smaller diameter on that caliber to allow for a little more meat in the cylinder, and barrels and cylinders from other calibers will not fit, nor will the 45LC OT cylinder and barrel fit on OT frames from other calibers.
If you just want 45LC then choose either the '60 R-M or the '72 OT in 45LC and you will be good to go. Thunderer grip frames will bolt on to either gun.
I'm not sure I understand your mention of the 44 Henry Flat in relation to the 45LC.
Hope that helps,
Abilene