I just bought a 84 C30 with a 454/400. It came with a tach and I am noticing its cruising at 3000 rpm going 65mpg on the freeway(4.10 gears) and will shift from 1-2 around 4200 and 2-3 at 4000. I know its a BB, but that seems like a very low rpm shift. I am wondering what other 454/400 are shifting at?