I think I'm gonna have to disagree. I am 99.9% sure they did not put Clevelands in 1969 Mustangs. The 351-4V is a Windsor. Either the engine in it is a Windsor, or it's not the original engine. The engines are very easy to tell apart. I have one of each in my garage at this moment. Both have around 300 hp. Anyways, look at the valve covers. How many valve cover bolts are there? There are 8 on a Cleveland, and 6 on a Windsor. If there are 8, it's either a Cleveland or they got those adaptor things and put Cleveland heads on a Windsor.
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Previously "BennyBoy"
'69 Coupe with 351W-I rolled it 8/8
Edelbrock RPM intake, Edelbrock RPM cam, Edelbrock 750 cfm carb, Hedman headers, 2 1/2" pipe, glasspacks, C4: shift kit, 9" Currie: Trac-Lok 3.70s, 290hp-stock heads
Starting Project "2ND COMING": 1969 Fastback