The 408" vs 426" debate!
I can give you two of the most important reasons why to stay with a 408" aside from the rod angle debate.
1. A 426" cost more to build than a 408" because they require custom pistons ($600-$700 over the 408" cost). If you need a replacement you'll wait months to get it over a shelf piston.
2. There are very, very few heads available that can properly provide the air flow a 408" needs, so when you build a 426" all you do is lower the potential RPM range the engine can make power at.
3. Having sold Molnar parts for 13 years and K1 prior to that I can tell you most guys just want a 426" because it sounds cool. Build the 408" and tell your friends it's a 426"
I'll sell a customer whatever they like, but I would never sell them a 426" without first explaining why a 408" is a much better engine combination.
Tom