Does your 1874 have the high-arch breechblock? And who did you have turn the barrels down and add the front sight bases? Always good to know who's doing that kind of work.
Parting together a rifle isn't all that bad, if the trades go right. Find (any) 1878 or later rifle with a rotted bore. Swap in a barreled action with a decent bore, fill out the parts as needed. I've done it a few times.
Next step up from there is to re-barrel a decent rifle with a rotted bore--takes a bit more work and a few more tools, but it is doable: with the loan of a pickup tailgate for a workbench, and a couple of hands to help hold things, I could have done it at the Grand Muster--can't do THAT with a Krag!
Building mixmasters has the benefit of saving collector-grade rifles for the collectors. There are times--it almost seems cyclical--when people seem to think trapdoors are worth as much as Sharps. I'm still looking for a shooter 1866, and have reconciled myself to parting one together. I did find a copy of Croft Barker's 5070 Shooters Handbook, so I figure I'm halfway there! But I'm thinking about changing my sig line to " Will trade 1878 trapdoor, brass, dies, moulds, for a decent 1866 and brass"!