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I spin my stock bottom 383 to 6400. no issues. 383's are pretty stout. remember that they have a forged crank and the same webbing / oiling / architecture as 440's and Hemi's, only with a smaller 3.38" stroke that does not tax this hardware nearly as hard as the RB's 3.75 stroke. I've always felt that the 383 was about as durable a workhorse as ever came out of an American auto maker.

It in't the bottom that will usually go. So what if they will spin 6000 or better not real likely with stock valve train that the valves will start to float on or the points distributor where the points will start to bounce. Even if you do get one that will spin that far what is the purpose. Bragging rights??? It is long done making power. Heck one of the first things we did with the magnums when new was to up grade the valve train to get rid of some of the float potential (we didn't like eyebrowed pistons or bent valves) and rework the distributor some.