GT Factory makes a 180degree hinge kit. When I worked at a shop we installed it on an 03 Denali. The kit is okay. The thing is when suiciding the rear doors is that there's not really enough spacing for the hinges to be stable and strong. OEM door hinges are spaced a ways apart, thus making them stable.
I'm not saying it can't be done, because it already has been on an 08 xB...
I'm not saying it can't be done, because it already has been on an 08 xB...

