V.I.N. Engine Code

I have a 1980 F250 with a 351 engine. I do not know how to tell if it is the 351 M or Windsor. I do know it is supposed to be in the VIN but can not find out for sure how
to read it since all the resources I find online require a 17 digit VIN and mine is only 11. My VIN is X25GKHD3704 Any help would be appreciated.
Thanks
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
look at the valve covers. if they have a raised part where the oil fill is, then drop down to a sort of flat cover, it is a 351M. if they are the same size full length, it is a 351W this is a picture of a 351M cover
http://i41.photobucket.com/albums/e261/tjctransport/351m.jpg and this is a pic of the 351W cover
http://i41.photobucket.com/albums/e261/tjctransport/351w.jpg
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Also, IIRC, the M will have the thermostat housing bolted to the block while the Windsor has the thermostat in the intake manifold....

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.