Can I replace my neck MIJ pickup with a Tex Special single coil and will the Mustang pickup cover fit the Tex Special?
Can you? yes, will the pickup cover fit? no, Texas specials have staggered poles, mustang singles are all flat.
Can you recommend a good neck pickup replacement for a Mustang that a cover will fit?
It would really depend on what you're looking for sound wise, vintage vs high output, though I never use the neck pickup in mine so it's still the stock one.
Something similar to a Texas Special. I'm putting a hotrail in the bridge and use the a lot too. Maybe I will just change the bridge and hear how it sound.
Thats what I do, I just don't care much for single coils. The only time I haven't minded them so far is in the affinity tele i got a couple weeks ago, those ones are fine, but generally they get swapped out quick for rails or a full size hummer.