04 6.0 temp, oil in fuel issues

I have a 2004 6.0L that I am having a couple issues with. October two years ago I went through and done a bunch of work to the engine. Head gaskets, studs, egr delete, oil cooler, injectors, coolant flush. This was around 190k. The truck now has 240k on it and I'm getting a big fuctuation in coolant temp and oil temp, up to 30+ degrees at times. I'm seeing a little water around the coolant cap, but not loosing much water if any. I'm also getting a little fuel in the oil somehow. I'm noticing that I'm gaining about a quart over 5k oil change. What are some issues that could be causing this?

Thanks in advance