I am about to run the water lines in our bathroom remodel.
The wife wants multiple shower heads, a hand held, water fall, and a fixed shower head.
Planning on using Kohler valve set K-693-K performance shower package.
I only have 1/2 water lines running to all my other fixtures right now, this valve requires 3/4 hot and cold lines.
Can I convert the 1/2 up to 3/4 inch from the old shower supply lines and have enough pressure?
If not what is the best solution.

can I convert the 1/2 up to 3/4 inch from the old shower supply lines and have enough pressure? If not what is the best solution
No! Increasing to 3/4" off a 1/2" feed would be the same as running 1/2" all the way. You can not choke the volume down to half inch and then expect to bring back the volume by increasing the size of the pipe to 3/4".
Run dedicated supplies off the hot and cold 3'4" mains. Good luck, Tom