The 408 builds I have looked into would likely require aftermarket heads (meaning $$$$) due to the crack issue with stock Magnum heads and the fact that you'd have to get the Magnum heads machined for LA-style intakes anyway.
1) I really wish this myth of all magnum heads cracking would go away. Its right up there with the factory overdrive slowing the vehicle down 1.5 seconds. rubbish. Some heads crack, no more than 906 heads cracking between exhaust ports. Millions of magnum motors are still on the road (my own truck has 161k and gets worked like a dog) none have ever ended up in my work bay because there was an issue with heads and I was a Dodge line tech.
2) There is several carb intakes available for the magnum heads, they are not hard to find. Mopar, Edelbrock and even the Chinese make a knockoff called crosswind with dual bolt pattern.
3) If you really are worried about heads you can buy the Aussie Enginequest magnum heads setup with valves and springs up to a 600 lift cam for under a grand, with or without LA bolt pattern. You can also get a cast iron Indy head for a little more money.
I have contemplated the same question with my '67 Dart shown in my signature line. The car is to be a fun street car with good brakes and decent handling.
The initial plan was to install a very healthy iron headed Magnum based engine between the rails.. but then I picked up a 400 motor.. and then a killer deal on Schumacher B/RB headers...
Weight wise it would pretty much be a wash between the iron head magnum engine and a 400 with aluminum heads and the Duster the headers came from ran mid-11's with a 440..
What to do?
