Josh,
I think a 292 with carry the SPA manifold and a T04 turbo. Remember the 292 is much taller than a 250.
The best pricing for the SPA manifold is at http://www.designengineering.com/catalog/spa-turbo-usa/turbo-manifolds/chevy

I can do measurements of a 292 with Parts on if needed.

Inliner Member 1716
65 Chevelle Wagon and 41 Hudson Pickup
Information and parts www.12bolt.com