I have decided to switch from factory loades to blackpowder in a Wesson & Harrington 1871 Buffalo Classic in 45-70. I read about a load of 65 gr. Goex FFFG---WLR primer---405 gr. bullet---with lubed felt Wonder Wad over the powder. Now the stupid question. Do I load this as I would a smokeless reload? Is this a safe load? Can you overload blackpowder as you can smokeless? Is their a good book on blackpowder reloading I should read first or load and go.

I think there is a sight for Black Powder Sillouette shooter where they discuss all of loading stuff that you are referring to.

A 45-70 was originally designed to shoot a .45 cal with 70grn.s of powder. You can't overload a cartridge with BP. The pressures are just not great enough to damage the weapon. Check with the cowboy action shooters. Many of them shoot BP only. The one thing to remember is to seat the bullet all the way down against the powder. You do not want the powder loose or a gap between the powder and bullet. This can cause the case to rupture.
Good Luck!