EDIT to add pics.
The BFG "KO" tires came out in the early 2000s after BFG Went bankrupt and their properties were acquired by Michelin.
ALSO EDIT<<<<I was wrong, that was th KO2s. The Treadwright Warden II is identical to the original BFGs you like.
Period correct for 77 would be the Goodyear Tracker A/T for factory (long discontinued because the tread had no lateral grooves, extremely prone to hydroplaning, no radial version was made when bias tires lost prominence).
A popular replacement tire from BFG was the Trail T/A. Also long discontinued, it was basically a consumer version of the still-popular-for-racing Baja T/A (which is about $1000 a tire).
A close match for the original tread pattern of the Trail T/A is the Mastercraft Wildcat A/T which is reasonably priced but can be hard to track down from time to time.
Another olde'-timey period correct-looking tread is the Toyo M55, which is a still-viable commercial traction tire, and it's kinda pricey because they never wear out, they harden up and dry-rot before the wear bars reach the road.