Needle setting has a big influence on plug color too, so like I said, make sure it's leaned a step.
Many consider the '76-'77 carb set one of the best of the 38s, so maybe that's why your buddy was running it. That's why I tried some on my '78. They are good but I think the original '78-'79 set is just as good, if not a little better. The needle mounting method was changed on the later set. The needle was spring-loaded and meters more precisely. This smooths out the carb's operation, especially at the lower end.