Hi
Len did a 400 for me. Interesting thing happened the trucking company dropped the crate in Augusta and it arrived upside down. Len insisted I send it back freight collect so he could make sure it was ok. He removed the heads to make sure the valves were not bent. He does stand by his work. I never got into any manifold or carb discussions but I did have Dan Fin of Fuel and Fire build a quadrajet to match engine specs. Dan was Aj Foyt's carb mechanic back in the day. I went with the RA factory type headers. Motor doesn't leak or burn oil.
My only complaint is I cant keep the rear tires on the road
I had a 70 challenger with a 383 and this engine is much faster. Hope this helps. Let me know how it goes. Based on my exp you will be happy.
Burt