With a lot of modifications, I guess you can mount them. But it still won't look right. If you look at the picture of the E70, the line under the top rear hatch continues with a bump in the taillight and goes on as a "bump" in the body, past the door handles etc.

Recreating that line in the bodywork of the E53 will take a lot of time and money, and still wouldn't look right. If you want the E70 taillights, it would be cheaper and better to sell your E53 and go buy a E70...

__________________
2004 BMW X5 3.0d
Safirschwarz metallic / Black Dakota leather