As for reproduction flintlocks, I'd recommend a former client of mine, Matt Avent, of Tennessee Valley Arms in Natchez, who makes an exquisite Tennessee and Kentucky flintlock. He made a left handed version for me that is a work of art in 54 caliber.
RE Shiloh/Flintlocks:
No doubt. There were thousands of them still available and in use. But the percussion lock was the already the standard issue.... And soon to be replaced by all-in-one metallic cartridges... like the Henry, Spencer, etc. used.
I’ve got two Hawken rifles, one perc in .54, one flintlock in .50. Love shooting black powder. Such a nice BOOM and wonderful cloud of smoke.