Stamey

I have a 1996 F500 with a 12v in it. I converted it into a dump truck. Besides the possible leaky injector, causing smoke when it starts after sitting for more then 4 days, the truck runs like champ and I don't know that I could be happier with it.
It has a 5 speed and weighs 13K empty.
I bought a 3K GSK but have not installed it because it works quite well as is. I'm not planning to up the fuel much since it hauls heavy loads (licensed for 26K), and I may not always be driving it.
I do plan to check the timing though, and while I'm in there, I might was well up it a little. How far should I go on the timing?
Oh, and I did get a set of stock 215hp 12v injectors, to replace the possibly leaky injector(s), so that's probably the extent of my additional fueling.

Thanks,
Chris