I agree Chris,
If you want an 100% accurate readout then an engine dyno is needed.
Do you have a chassis Dyno in denmark that will take the power you are wanting to run, as I can see serious traction issues being encounted.
Wish you the best of luck though, I just hope its lasts long as 70k would be horriable to lose after a few dyno pulls.
Ryan
p.s i reckon if Paul whiffin turned up his boost and applied abit of nitrous he would be knocking on the door of 1300bhp. But i doubt he will as it seems he has a reliable 850bhp at present so why lose it.