I cast and shoot plain base bullets in my 45/70 Sharps. I've used a 490 grain tapered and the standard Gov't bullet molds (both Lyman). I just cast using straight WW. Homemade pan-lubed with 60/40 Crisco/beeswax.
I get great results with 23 grains IMR SR4759, it is very accurate. My second choice is IMR 4227.
I use either large pistol primer or LR primers, a 1/4 sheet of t-paper wad over the powder, and a LDPE wad under the bullet.
Hope this helps,
Darryl