How to stress test my " possibly damaged cpu"?

P95 is as good a stress test as there is. Maybe add Intel Burn Test to your collection, too.
Is your cooler working as it should? Fan not bogged down?
These are the recommended safe temps for the Q6600 depending on which you have:
5°C - 62.2°C (Stepping B3)
5°C - 71°C (Stepping G0)

Opps. My bad. I didn't see the 'K' on the end and thought you had an old Q6600. Sorry.
In that case, you'll want to go by this:
Tcase (CPU temp) = 64C
Tjunction (Core temp) = 69C
Tj Max (Throttle temp) = 100C
http://www.tomshardware.com/forum/id-1800828/intel-temperature-guide.html

Was the old CPU running those high max temps?
How are the H60 pump and rad fan connected?

OK. But I meant where were the fan and pump connected. Many folks make the mistake of plugging the pump into the cpu-fan header and the fan into some sys-fan header.

i really wouldn't worry on thermal damage - intel's cpus have a 100C thermal throttle limit built in, so it will decrease the load for a few seconds to bring the temp back down. On my first build, i was using the stock intel cooler and relying on Asus's AI Suite performance utility which was showing cpu temps never exceeding 67C.

i rendered videos for 3+ months, but noticed the computer would slow down at times. Then i saw a thread where someone complained the Asus performance utility was corrupt and showing heat or temp values way off. So i downloaded RealTempGT monitoring utility and it was showing 100C - cpu would run 96C to 100C then fall right back to 96C, and climb right back to 100C, and repeat endlessly, while rendering videos. Average video file took back then 75-85 minutes to render, and Handbrake is a core hog, showing 98-99% load in all four cores. I tested with a couple of other utilities including Intel's Extreme Tuning Utility, and all showed the same high temps kissing the throttle limit. So for 3 months i had been running my cpu flat out at the temp limit.

I deleted Asus's utility, went thru the system to see what in the hell was wrong, and found the intel cooler had one pin that would not stay locked, meaning the heatsink was not in full contact with the cpu. But needless to say i was worried i had damaged my cpu.

I upgraded the cooler, am now running temps that max at 63C, and when i run a benchmark using intel's ETU and then let the utility upload the results to HWBOT to compare to other users, the benchmark consistently places in the top 5% of other users running the same mobo and cpu - and this is two years after discovering the Asus utility was lying to me.

Those same videos now render in 35-45 minutes, and i generally do 5-10 a week.

Plus, i doubt the discoloration was from cpu temps - i work with metal, and it takes, depending on the alloy, 400-900 degress F to discolor stainless steel. Additionally, i've never seen stainless discolor orange from heat, usually blue and some black. Those orange spots are probably from the heat paste, maybe there was some contamination in it or one of the compounds in it turn orange naturally from heat.

FWIW

sorry to chime in late, i agree with the original ralph i wouldnt be worried about it. btw just to address the fan plugs, the opt. one is in case you have 2 cpu fans like on my noctua cooler, or a liquid cooler. (which your h60 is) so feel free to put it there. honestly though if your really concerned about it. the prime 95 test is there for a reason, use it for an hour no o.c. and if it fails send it back to intel as defective but the previous posters are correct your tj max is pretty high up there so i wouldnt be concerned about 70's c remember this test is meant to push it to its max.