You aren't gonna get very far w/an M. There aren't many pistons available and what you can find won't get reasonable compression - about 8.0:1. But, if you put a 400 crank in it you can run Tim's pistons and get 9.5:1 and you'll have something that'll run.

 

Not going that far, no new pistons, none of that. I have done the numbers for what I want, I can have my guy build me a nice 302 or a 351W for a lot less, or even buy a Ford Racing mild crate and be ahead. Or I can do some mild up dates to the M and make it a little better, cause anything is better than now. You say "run", but you are you and what you want is not what I want. A good, breathing 302 will give me plenty for what I will do with the Ranchero.
Have an extra Edelbrock Performer intake, one for a 302, one for 351W, have another 1406 carb, etc, setting on the shelf, cams are cheap, for what I want, and 8.5 is all the compression I require for what I desire.

 

You are aware that the Windsors have a different bell housing than the 335 Series I assume. And that the perches in your truck are specific to the M/400? Windsors are good motors, but changing from an M to a W isn't bolt-in.