The boss heads have canted valves. They where not 351 heads. If they have canted valves then they are boss heads. 351 clevelands came out with canted valves in 1970. A boss 302 is also a 4 bolt main block regular 302 blocks aren't. A boss also has a stronger crank.
As for your other questions i can't answer i am not very good at tunning a car. I do know that if your car is running really rich you can smell gas on the spark plugs.
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428 Cobra Jet
SOHC 5.4 3V F-150
96 mystic cobra
91 GT
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