Engine casting number

I have a 69 Mustang Fastback. Trying to find out what engine is in this car. The win number calls for a 351. When I changed the intake manifold gasket, the only one that would fit was for a 302 Boss. The block number is D1AE-6015-DA12. Anybody know what I have?
Thanks Milan

I am no expert on casting numbers, but I do know the Boss 302 and the Cleveland had similar head castings. It's quite possibly a Cleveland. You can tell a Cleveland from a Windsor by where the radiator hose connects to the engine. The Windsor goes into the intake manifold and the Cleveland does not. The Cleveland also uses 14 mm plugs vs. the 5/8" plugs in the Windsor. Also, the D1 would indicate a 1971 casting vs. 1969 so it is not the original block that came with the car. Poke around in this site, there's all kinds of Mustang info in here.

http://links.vintage-mustang.com/index.html

Here's some other info I ran across from www.mustangsandmore.com

The first two digits indicate year. The letter is the decade;
A = '40s
B = '50s
C = '60s
D = '70s
E = '80s
F = '90s
G = '00s

The third digit designates body line;
A = Ford full size
D = Falcon
E = Escort
F = Pinto, Maverick, Falcon
G = Early Comets, Montego, Cyclone
H = Medium/Heavy Duty Truck
K = Edsel
L = Lincoln Mark VII
M = Mercury
O = Fairlane
R = Capri
S = Thunderbird
T = Pick-up Truck or Bronco
U = Econoline Van
V = Lincoln
W = Cougar
Z = Mustang
{there are actually many more}

The fourth position signifies Engineering group;
A = Chassis
B = Body
E = Engine

If it's a Service Replacement part;
Z = Ford Division
Y = Lincoln-Mercury
X = Original Muscle Parts program
M = Ford Motorsport, SVO, FFRP

The center number, four or more numbers or letters, is the part number.
The A at the end of the number indicates that the part is the first version. If it was revised once, it would be B. If it was revised again, it would be C, and so on. When they run out of letters, it becomes AA, AB, and so on.


This link may help too. http://www.classicmustang.com/casting_numbers.htm
Based on that info you have a 71 302