You could start with the stock 440 cam for a baseline, the stock cams typically do well in turbo applications. You could also check a few of the big manufacturers for recommendations. Crower has two turbo-specific grinds for small blocks, which I ASSume you could have ground on big block blanks. I wasn't shopping for big block stuff back when I was doing my turbo research, so you'll have to check on that yourself.
Crower PN 31978
Crower PN 31978

They might even want to brew up something a little hotter than these two for a 440, although it's tough to go too mild on a turbo cam.

FWIW, I was planning on a single HX-40 for my 318. On paper it was making 400hp/425lbft at 8psi with the -78 cam, and 450hp/430lbft with the -79 cam. I've been using Ray Hall's site for tinkering. Desk Top Dyno 2000 seems to have some "issues" with turbo applications, even for a go-by.

Clair