I think King bought BH in 1990, may have been 91, honestly dont remember if asbell started the flat limb bed, he may have, would of been right before the sale.
King improved the flatbed with a better bolt system,
Im sure there are others here that can be more accurate with dates etc.
I was privy to see some one of a kind Big Horns back in the early days , one was a latch system td , like the bear bows, some pretty crazy grips on Freds personal bows, if you look closely at Freds pictures you can see some