The thin wall block rumour is a myth as well. You could go and sonic scan any 400 block and it wont be that bad. Not many of them were so badly core shifted as to need sleeving.Probably no better or worse than any other block in that respect.
Go and ask any decent engine builder that knows mopar and they will tell you to build a 400 block up if you want to make better than 650 h.p without buyinf an aftermarket block. If they want to use a 440 block,run away.
