351 How can I tell what version it is, 351 W, C, or M??

Have a 1992 F150 scab 4x4 with 5.8L.

Originally had a 302, previous owner switched out to a long block 351. My question is. How can I tell what version it is, 351 W, C, or M? I want to buy a gasket set for it but not sure which version, didn't know if there was a tell tale way to tell.

Second question

a few weeks ago the passenger side window won't roll down anymore, it don't even make any noise? Is this more than likely the motor or the relay? Where can I find the relay for it at?

Thanks in advance