You had better talk to your crank guy about that .275 destroke. I'd bet you can't cut it that much.
I think the most you could destroke it, and still use a bbc rod is .205, and that's if the crank grinder is perfect.
To destroke more than that, you'd have to use something else, maybe a long small block rod. I don't think you can find a small block rod long enough, unless you go to a custom aluminum rod. And the crank would be seriously thin, if it doesn't already have a "window".