I shoot BPCR with a .38-55 and .40-65.
Lyman 358674 335 grain is good in my rebored barrel with 15" twist. A stock 18" twist might not stabilize it (but one source says it will.)
The Lyman 410663 400 grain Snover is great in .40-65, not much to beat it until you start getting into some of the "NASA" designs.
I don't shoot .45-70 but one of the Creedmoor or Postell styles would be good, and the original 500 grain government design nearly always works.
If you don't mind paying for a custom mould, Paul Jones makes the best I have seen.
I have cast bullets out of 20:1 lead:tin alloy; most BPCR shooters favor that or something a bit softer down to 25:1 or 30:1. A paper patch loader will go as soft as 40:1. I don't know anybody using pure lead, a little tin helps the casting as well as hardening the alloy a bit.
I have bought bullets made with antimonial lead and they do ok, but would not use it myself.
Wheelweights are inconsistent and linotype is way harder than you want for BPCR.