225 to 400

I want to go for a big block with 727 and an 8 3/4 rear end. I'm happy with the stock power of a big block in an A body. Here is a picture of the 400 that would be a possibility for me. Please give me your honest opinion on it. The guy wanted 500 but I haven't given him a counter offer yet. He said it came out of a 72 or 73 newport with 70XXX miles and he says its complete without the carb. and exhaust. Thanks for all the help everyone!!