If you are sure winning isn’t in the cards, then it depends on what your initial goal with the race was and whether you have adjusted it given the reality of your untimely illness. It also depends on how quickly your illness concludes, since it sounds like you aren’t all the way through it yet.
Assuming your goal is best possible performance on race day:
Were I in your shoes, I would do a “test balloon” ride on one of the lower intensity sessions I know very well like Petit or Mount Field or Baxter – let that effort tell me whether my body is ready to work. If it isn’t, I’d rest another day or two and then try again. Your best training right now is full recovery from your illness.
Assuming you feel like all systems are go, then all you can do in 8 days is two or three efforts to sharpen and wake your legs back up. There is no fitness to gain, so there is absolutely no reason to bury yourself. Grab a couple of the 30-45 minute sharpening workouts and throw them in the week before the race. Just enough to wake up your legs and remind you what “hard” feels like – not enough to run up a deficit.
This could be a cool opportunity to look in the mirror and say “to hell with my result” and play with process goals or to ride a tactically very different race just to see how it plays out. A 50 mile rolling race is going to give you lots of chances to practice attacking (even if you are off the back, you won’t be alone) or bridging or any number of skills that could help you win a race in the future.
Sorry about the bum luck getting sick!