I have 408 from Blueprint with the iron Magnum heads. Got it in 2009. I have 5K miles on it. It runs very strong and is frankly all I need for a driver car. It is a torque oriented motor and fun to drive on the street. It isn't faster than EVERY car on the road of course (esp with all the high HP new Mustangs, SRT8 Challengers, etc out there), but for the money and time saved by getting a ready built package to me it is a good deal.
Hear it running here:
http://www.youtube.com/watch?v=H9Wzbd9Y4OU
About 14 seconds in, you see why I like the torque on this engine!
Here is the idle:
http://www.youtube.com/watch?v=r3vUXmQ6RN0
http://www.youtube.com/watch?v=ZNU_vvCyXsw
In my humble opinion, you roll the dice with any choice. You can use the internet and forums to prove whatever point you want. I find the internet is good to give you the extremes of good and bad, but mostly the bad - people feel they got screwed and want to vent (and rightly so). In my view, the vast majority of satisfied people with whatever product you name don't ever say a word and don't post reviews or give feedback..... be the product lawnmowers, cell phones, video cameras, OR crate engines. I have friends who got screwed with a custom built engine (turned into a money drain, took forEVER, no warranty, etc) and others who got screwed with a crate engine.
One choice that might be safer but filled with its own problems is to go with a modern Hemi engine that gives you all the benefits of modern technology. Those old engines, crate or custom are old technology and they leak and wear faster than the new engines. I like the old engines and that is what I used of course but as I said I think there is a possible downside whatever you do.
My 2 cents worth.