The block in your pictures is not a 400, it is a 440 block with the last three numbers in the casting number "440", not "400". The supposidely(SP?) best 400 blocks are the cold weather)1971 castings from June of 1971 to September or October "230" castings with the really large casting numbers, the others after that are the 3614230 casting numbers used up to around 1973 or 1974. The casting numbers I have on 400 blcoks after that are either 400530-400-1 or -2 castings All Mopar blocks should have a casting date on one side like 12-9-75 or 2-16-72 That will tell you the day, month and year that block was cast in All 400 BLOCKS should have all the cylinders sonic tested before boring I had a 230 casting(not sonic tested properly ) split a cylinder wall on the dyno, it had really bad core shift on the drivers side and wasn't saveable IHTHs