Sounds great,however I am very leary over loads of unique in the .45/70. Nasty to ring a chamber, it would be, said Oda.

The Trail Boss and 5744 loads would be my direction for reduced velocity loads.
56744 is capable of loading to over BP ballistics or wherever you want them.

The idea of a .30/06 cast bullet DR sounds fun.

With cast bullets the intent, you might want to pick up a tub of JB Compound and really polish up the throat with it. Auto-Sol or Flitz will be the same thing.

A cast bullet, lubed and gas checked that just fits the fired case, might give you the best accuracy.
My late cousin Ed. used a .308 as his match rifle for decades- using cast bullets sized to .311". Eddie did very well with it & that rifle easily grouped an inch at 100 yards with his loads.

Deprime, re-prime, dump powder and seat a bullet.