misfire p0305 and p0200

[JimBobMcCready]

My tahoe is misfiring badly. It was run until it overheated. A couple of days later, after it was refilled with water, it started knocking and throwing off codes. I idles okay for a little while, and in park it doesn't knock that I can hear.
When it is under load, acceleration, steady speeds over about 15mph it knocks badly.

I have replaced the knock sensor, and while it was in bad shape, didn't seem to be causing the problem. I have checked the resistance of the plug wires and they seem to be very low >2000ohms.
Sparkplug has been changed in the 5th cylinder.
I put a timing light on it and it seems that the timing is way off. The mark on the damper is way left of the scale, probably more than one inch.

I am stumped
I am not sure, but it might be leaking some coolant, from where I cannot tell.

What can cause these codes?Thanks
Kurt

[JimBobMcCready]

subject says -0200, should be code p0300