Mine has a 351W but I didnt install it, it was in there when I bought it so yes it can be done but sorry if I cant be more help then that or anything to do w/ the mounts.
what is your combo on the windsor? i know several people on here have done this swap and i haven't heard of anyone having this problem. this kinda makes me curious to know what kind of transmission and k member you got, and it may have something to do with the fitmit of those.
i'm sorry i wasnt anymore help than this but i'm just thinking out loud. hope you get everything sorted out and make sure to keep this thread up because i am interested in this subject and i will be doing this swap by the end of this year.
I have a 351w and originally tried fitting a tubular k-member.
The k-member had two slots for motor mounts on each side. The front facing mount locations cleared the firewall, but the headers hit the steering shaft.
The rear facing mount position put the engine up aginst the firewall making the air tube hit (could have removed air tube to fit). But the biggest problem was that the LT headers hit the lower part of the fire wall and the STB hit the rear part of intake.
I never had any problems with mine, but I installed the engine and trans separately. You need to use 302 motor mounts, the 351 is the same engine just taller and wider.
Here's pics of both mounts. I don't have a tubular k-member in these pics, but I have one now and had no problems installing it.
I used a QA1 k-member in my S-351. Everything fit fine. The only thing I will tell you that will be an issue is the headers. You can not use Fox body long tube headers. I have never heard of anyone having this issue with a 351w swap. You might want to check to make sure you receved the right k-member and not one for a 4.6 car or one that was just made wrong. Mine has 2 slots in it also and I could even use the rear slots to set my motor down in the car. It would put the motor damn near against the firewall though. Check also to make sure you have the right mounts for the right side. Getting them on the wrong side will cause this issue.
I had the exact same problems with my setup. My K-member had two slots available for the motor mount studs to install into. The furthest forward slot would not allow the passenger header to fit correctly (the steering linkage was not hooked up so I have no idea on clearance there) and the slot closest to the firewall would force the headers and the blower to hit the firewall. I ended up fabricating a new mount.