If you cant ride the actual climbs, you could ride the route/climbs using Bkool on your Smart Trainer.
This would allow you to work out estimated times for various sections/climbs.
Then use goal times with Strava Segments.
Maybe break up the big climbs into say 10km sections and ride them at a set time using Strava Goal for pacing.
Have a look at the climbs on Strava and see what people/friends you are similar to in terms of speed/ability are climbing at and then set goal times and try to ride to that pace.
Im doing Peaks Challenge in Australia next year which is 235km and 4500 metres climbing roughly. I have power meter and have just come back from riding the main climbs so now I have an understanding of my times but could get a basic idea using Bkool as well.
I have a power meter and will use Best Bike Split for pacing strategy. While I was climbing individual climbs at 0.8 to 0.9 IF, obviously i will be going a lot easier on event day as it will be a 10 hour event for me.
Hope this helps. Im not a expert, so take this with a grain of salt. 