Summit Racing has the best customer service in the business. Don't buy from Jegs, they are rude and condescending to their customers and don't know the meaning of customer service. I have dealt with Summit for 25 years without a single problem.
I was just getting ready to purchase the 572 aluminum Hemi from Indy Heads and I am glad that I checked the blogs first. It seems that very few people have anything good to say about them and that surprises me. Same with Ray Barton, very few have anything good to say about him either.
I have read that Stanton Racing in KY seems to be the prefered builder. He also now builds the 426 crate Hemis for Mopar as well as the new style 426 Hemi small blocks making 600 HP.