Yes, you can use the Pyrodex pellets.
I just looked through my latest Hodgdon Pyrodex load booklet. They show Pyrodex pellet data for .44 Remington Magnum, .44-40 WCF, .45 Long Colt, and .45-70 Government. I may try one of their .45-70 Government loads, it specifies 2 each of the 50/30 pellets behind a 405gr RNFP bullet, for 1270fps.
"Bother", said Pooh, as he chambered another round...