1971 dart and 1969 merc cyclone

Hey I learned how to cut and paste from the internet too...
IDENTIFYING 351 WINDSOR AND 351 CLEVELAND ENGINES
We receive many phone calls from classic Mustang enthusiasts inquiring if the engine in their 1969 or 1970 Mustang or the 1969 or 1970 Mustang they are contemplating purchasing is a 351 V-8 Windsor or a 351 V-8 Cleveland. First of all, virtually all 1969 351 V-8 engines were Windsors and virtually all 1970 351 V-8 engines were Clevelands. There are a few exceptions. Over the years we have seen a few 1969 Mustangs with factory installed Cleveland engines. By checking the build dates of these Cleveland 1969?s we found that in every case these Mustangs were produced in the last week or two of 1969 production when perhaps the factory ran out of Windsor engines. Conversely, we have also seen very early production 1970 Mustangs equipped with 351 V-8 Windsor engines. Again, perhaps the producing factory was using up their supply of Windsor engines before beginning Cleveland engine production. In either case we have found these to be very rare occurrences.