the paperwork i got with my 429 a few weeks ago says, the D1VE AA blocks were produced in the michigan flatrock foundry from 1971 to 1978. the D1VE AA blocks have a narrower oil pan rail. the DOVE-A blocks produced in the dearborn factory were the only blocks cast with the extra thick main cap webbing allowing for 4 bolt main caps. the DOVE blocks were the CJ and SCJ blocks. it also says they tested 30 different 429 blocks with various casting numbers for ultra sonic thickness, and no block was superior to the other in cylinder wall thickness, the only difference was for the 4 bolt main cap. unless you are throwing over 500 horses into it it is a good buy.