Not sure when they changed it, but the p/w circuit breaker for my '74 is under the hood, on the firewall.
The fuse box is held on by a single bolt from the engine side, where the harness goes thru, under the brake master cyl/power booster. It's a 3/8" bolt, if I remember correctly. Once this bolt is loosened, the fuse box can be pulled away from the firewall from the inside. Don't expect it to just fall off tho...
Your's may have a couple of screws on the inside too, holding it to the firewall, but I don't recall ever seeing one like that....but I haven't had the pleasure of standing on my head under the dash of many '76s!
hth
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Joel Adams
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