Custom frame

I just purchased a 79 kz750 fours and I am wondering how I should go about customizing frame so that I can convert it to a single suspension and raise it up a little. Open to anything thank you.

If by single suspension you mean a mono-shock swingarm, there are a couple of build threads around here, but they are probably archived, so you will need to spend some time with the search function. Larry Cavenaugh's 1979 LTD comes to mind.
If you mean a single sided swingarm and mono-shock, you may be on your own.
The builds I remember were on 1000cc machines, so yours may be a little different.

monoshock conversion would usually entail a donor swing arm, wheel casliper etc etc. and some good welding fabrication skills. Battery / airbox may need to move .

If you are asking how-to you might be better getting one that has already been built.

Fitting longer rear twin shocks - up to 1 inch over works for me and quickens up the turn-in steering. Also they look better slighly jacked up imo.