Even though the specs might be the same, it will most likely not run optimal.
In your case, even the specifications of the two types are not the same, thus one of them may not run as it should.
I am not sure what you mean by CPU MP. I have the host clock set at 450MHz, and the RAM at 1:1 is getting at 450MHz. Or do you mean to go back on my CPU/FSB overclock and stress the RAM in isolation? That sounds like a good suggestion if you can confirm
I was more worried about the CPU Termination / MCH and RAM voltages. Do you think any of these is getting over the board right now? Also, do you recommend I keep the timings as relaxed as 6-6-6-18 for further testing?
If you lower just this, and keep the rest of your settings the same, you are excluding the CPU from failing in a stresstest.
In this way you will be testing your RAM modules for if you have a stable OC.
What I would advise you is to take out one kind of RAM modules, and test just with the other.
Wich one you take out isn't really an issue now Later you could switch to whichever modules you'd like.
I must admit, it has been quite some time since my own LGA775 platform so I cant say for shure if the voltages that you are doubting are good, but they seem fine to me. Fine in a way that they shouldn't cause instabillity, maybe they're a bit high, but can't really recall.