also, i was looking at darts small block 400. are these different from the originals? and would it be safe to bore it to a 406? i know the 400 was bad on over heating because of the siamesed water jackets. so im a little worried about boring it and using it it my build. i was reading a article in chevy hi performance. ''muscle mouse'' and the numbers their engine put out are exactly what i want, so i want to build one like theirs, but would it be safe to use?