To me, the possibility of using a non-collector Model 1886 T/D configuration & spiffing it up as desired; such seems far more practical! Strong upside of acquiring T/D as fACTORY- "done deal as manufactured!" Such assurance of 'pro' v/s Bubba. That plus, huge potential savings of time & effort as quality made of inception! Avoiding reinventing the wheel and fussing in the processl!
Downside 'if' you're into hot loads, where Model 71 Chrome Moly steel suggesting definitely desirability edge. Otherwise, consider that the entire Model 71 design factors aren't so much different than the '86. The typical straight grip stock of the '86 if not to suit, adaption there perhaps if not able to find a classic '86 pistol grip stock of origin.
0ne of the main features sough by me 'if' engaging in such project, to achieve a more modern & available cartridge than the 348 Win or the 33 Win chambering. The 45/70 as likely candidate beckoning!
No gunsmith here, simply my thoughts. Such where "hypothetical projects" fall by the wayside due to the realities of contemporary inflation & cost/benefit ratio!
Good luck & just my take!
Best!
John