i don't think you can make a nikon to K mount as the nikons rear to film plane is too small. i did see a smc 500mm/f4.5 with a nikon mount but it had at least one lens in it for correcting the focal distance. i may be wrong. i'm not sure if sigma and tamron make one for pentax but both of them do make a 180mm 1:1 macro. i do know that they sell for under $1000.