i am pretty sure d is 70,s/ 4 is the yr. / is the ae body type designed for? / dont know what the 6015 is (block part number)? / aa7 i have no idea, also under this casting to the right is 4L8 any meaning. please help, motor runs great, i have pulled out and cleaning and paint,is this a good block or not, guy i got the car from said it was out of a late70,s truck. i am clueless.thank you in advance

Brad, you are right about the number breakdown. The 4L8 is the date of the casting (November 8th, 1974), AA7 is the change level.

In my opinion, any 351 Windsor block is good. No problem at all using that block.

guess i didnt look hard enough, anyway, i found out d is 70s,4 is year, A is body type originally designed for galaxy line also used in full size trucks(not sure about that year74), E is engine engineering dept., 6015 general part number, date decode 4 is year-L is oct.-8 is day. on the design change suffix denotes i have found that A is for 289/302, also A is first level of change, C is for 351c,4vmotor. soooooo curiosity is killin me. should i be assuming that AA7 was just certain changes made to the block at the first level of design changes. IS THERE ANY WAY TO FIND OUT EXACTLY WHAT THESE CHANGES WAS? this info above i found at TMS(the mustang shop) and classic mustang.com. thanks again, just curious