What would be the best kit for putting a solid axle under a 92 f150  

go with a fullsize d44 bronco from the late 70s  

just make sure you take all the other crap like radius arms, all brackets, trackbar & mount so on and so forth  

if you find the right front f150 solid front it will be almost a bolt in swap. we just did one here in our shop. i dont have specs in front of me here, but i will find out at work and post it on here  

76-79 F150 non supercab or 78-79 bronco. 75's most still had drum brakes 76 up f-150 were all disc 78-79 had the best sterring set up from the factory but thats easy to update.76-77 had tri-y good for the death wobble