The .38spl was introduced in 1899 as a black powder cartridge and it was only about a year later when it began being loaded with smokeless. I have had great results with loads using both 3F real BP and T-7. Go with about 0.030" compression on the real BP and snug but no compression on the T-7.
The original .38spl bullet was a 160gr nearly pure lead RN, neither Lyman nor Lee RN molds have the correct original bullet design. There is at least a couple sole-proprietor mold makers makers that do offer the correct (or nearly so) original bullet design which is a true RN and not the common elongated ogive RN's offered by Lee & Lyman. If you're looking for top accuracy, you're going to have to lap out production mold to cast the proper size using pure lead, if you get the mold made by one of the sole-proprietor shops, they can make the mold the correct size right from the start. I use the Lee 158RF mold lapped out to drop bullets at 0.359" with almost pure lead, makes a good accurate all-around bullet but is not historically correct.
The .38 Short Colt used a 130gr dual-diameter heeled bullet, heel smaller in diameter and seated in the case, the exposed portion of the bullet was the same diameter as the case just like a .22LR round. The .38 Short Colt was for use in the converted .36cal C&B revolvers. The .38 Long Colt used a single-diameter bullet 0.357" in diameter, they were not intended for use in converted C&B's and the accuracy problems in the early Colt cartridge revolvers resulted from the lack of proper chambering, the entire cylinder was bored to case diameter.
You can get 3/8" thick fiber wads from Circlefly that make for really nice light plinking loads. .357mag chambers allow for using the magnum-length case which is a fairly potent load with BP.