I agree with the Dart tech for the 308s. A friend of mine has a 489 BBC and is making 846 hp on the dyno with his 308s and a Brodix intake manifold. He had a set of 345s last year, but his engine guy said they were too big and go to the 308s which had better velocity for his cubic inch. He did and he picked up quite a bit of hp. His motor is a single 4 gas dominator carb and 13.6 compression.