I'm doing something similar, but replacing an old OHC 6 with a DOHC 4V inline 6. The basis for my swap is the Vortec 4200, which is akin to a long-stroke/large bore EcoTec. The engine that inspired me to do this swap made 1365hp with a GT47R. I'm going for streetability using a GT42R. I plan to run the living piss out of this at any event or track that I can, so I started with the chassis first.
Here's an older pic with the mock-up engine in place & modified front frame:
