I'm still waiting on my Liberty Cosmic to get out of jail, but I've already bought a Ruger 77/44 to host it.
I've been thinking that 300gr subsonics won't cut it...

Would the TC have enough meat on the barrel to thread? Would those 500+ grain bullets be quiet through my can?

No idea about the meat on the barrel for threading, but looks fun..

405gr subsonic

45/70 does not suppress as well as you might think.  It requires more powder and therefore more volume to get equal velocities.  Therefore, you need a higher volume can and that kinda takes you out of 45 ACP suppressors.  Yeah, you can get a longer bullet, but unlike 45 Colt based chamber with a straight wall, you can't really shorten the 45/70.  My advice would be to get the 454 or 460 barrel so you can run shorter brass, lower volume loads to tune your subsonics.  I think Beartooth Bullets has some good heavy loads, but their site is down right now.  One very good thing about the .460 barrels is that they are 1-in-16 twist for the heavier bullets.  I'm sticking with 44 magnum for now and was using 300's but want to try some 405 gr loads.

I didn't think about that. I could use .45lc brass and load a really long bullet, right?

Or even Schofield or Casull brass.  Whatever floats your boat.  I don't have any experience with the 45 calibers for suppressed fire.  I do have a 45/70 contender and am probably going to sell off the barrel to get something more practical.  Probably another 44 magnum.  Just note that they don't make the 460 for the contender, only the Encore.

I'm still confused on all of the variations. G2, contender, encore, pro hunter, katahdin....

For new guns, only two variations.  One is the G2 (generation 2) Contender.  The other is the Encore.  The other names are just model variations.  All G2  barrels are interchangeable and all Encore barrels are interchangeable.

I've got a kahatadin 45-70 Ill be threading soon.  Yes, it has enough meat on the barrel to thread.     I've also got a marlin 45-70 threaded.  Just waiting on my hybrid on both.  From what I've seen on videos, it's worth it to thread them to reduce recoil and it does have a reduction in sound.  I plan on starting with supers but as time goes on, I'll load for subs.     I've also got a 458 tromix upper coming too.  do some searches on youtube for the thompson suppressed.  I think I've seen a few.

Ok, thanks. That helps.

Please keep us updated. I'm interested in the outcome.

I've toyed with the idea. It seems the Contender is a bit light for the .45-70. It's fine if you only plan to shoot subs or lower pressure loads. The hotter loads are better suited to the Encore, Ruger #1, or other stronger actions.

As noted, if you want to go heavy, make sure whatever you get has a fade enough twist barrel.

I've got a number of Contender barrels threaded for suppressors, but .44 Mag is the largest I've ever done.

I've already got a suppressed 458 SOCOM and I just sent my 45/70 Encore barrel out for threading this week. I've got a few cans of trailboss and I'll probably get some 300 or 405 gr rounds loaded before the barrel gets back.