This thread has some good info on the race and what to expect.
I’ll be doing the 50k for the 3rd time. It’s hard, but very doable if you pace yourself. My w/kg was similar to yours the first time I did it and it took me almost 4 hours.
To me it’s all about the final climb. Just make sure you leave something in the tank for it. Try not to push too hard on the other climbs, stay on top of your nutrition, and ride the non climbing sections really easy.