Ok... here it goes.
Download these to begin with while you READ.
IT IS IMPORTANT THAT YOU READ EVERYTHING I WRITE.
The problem is that the device has conflicting spl and radio combo. The spl has an idea of where the radio should be and how big ect. When they are not matching the flash of a new radio will most likely fail.
To fix this problem, we need to flash a spl compatible with the 6.35 radio.
But the problem lies in the following. All the RUU/sappimg with a spl compatible with the 6.35 has a higher version than yours(starts with 3 something). If we update the version, we cannot flash the desired sappimg which follows. The goldcard will only update up in verion nr, NOT down.
Here comes the trick: We don't let it update the version nr :0)
The special sappimg.zip is part of a 2 step update from HTC. The first part (which i have given you) will update spl, radio and boot partitions only and then restart. It will not touch the version nr until the second part is applied. Well.. we don't need the second part, because by now we have matching spl/radio combo.
Once the spl is updated and the system restarted, we can now flash any ruu we want using the goldcard. We could flash the sappimg.zip with a eng spl inbuilt like the 2.53.707.2 sappimg. Or, just flash stock MT3G 32A 3.5 MM rom.
The steps to follow:
1) Read and understand the above.
2) Rename special_sappimg.zip to sappimg.zip
3) Make sure that you have a working goldcard and flash the sappimg.zip
The device should reboot by it's self. If you get any error saying model id is no correct, you have a faulty goldcard. Also, please verify that the spl has changed to 1.76.xxxx. (flash by holding volume decrease (-) together with power and wait for the hboot to automatically pick up the file)
4) Once the device has rebooted, you should rename the 2.53.707.2_-_sappimg.zip to sappimg.zip and flash it using the goldcard. This image should give you an eng spl. If you device will not accept it/or you wish to have stock image, then rename the stock sappimg(2.10.531.4) to sappimg.zip and flash it the same way as the special sappimg.
5) If you indeed get the eng spl, then you have full control and we can do almost anything we want. Just post here and we can take it from there. The eng spl has the following nr: 1.33.2010.
If you flashed the stock sappimg, then you only need to root and flash custom recovery and you should almost be there... also here post the progress and we will take it from there.
Hope that you will succeed... Good luck :0)