I have a K3, with both a bar conversion and a front end swap. The whole job cost more than my bike is probably worth, but she looks amazing and rides beautifully. However, I made the swaps because I have a disability and could no longer bend over clip on bars and needed very soft suspension to ease further back pain. You can find my whole build thread
here.
I used a set of R1 forks (purchased on here), with GSXR yokes that I had machined and then had risers fitted to. The forks were stripped and rebuilt by MCT with a mix of Maxton and Ohlins internals. I have upgraded brakes because I have weak and arthritic hands and appreciate the extra braking power. I am currently thinking about changes I can make to the cutch because on long rides, I struggle to pull the clutch lever. The biggest tip I have for you is don't grow old. Stay young forever!