OP, you might evaluate a Cervelo R3. It’s designed for exactly what you’re intending. The headset is a little taller which is really nice for both longer climbs and overall comfort. Cervelo makes one of the lighter frame sets but they are also pretty stiff where they need to be (bottom bracket) which produces an overall very smooth ride. I’ve ridden many centuries, lots of hilly rides and even across the US on one of mine. If you shop a little you should be able to find a new previous years model at a greatly reduced price. I’ve ridden some other stiff bikes and they picked up way too many road bumps. Those bumps will travel up your back and can really wear you out in just a few hours. If you add a little wider rims with 25 mm tires, you can run 80 psi in the tires even with tubes. It’s an awesome comfy ride and doesn’t sacrifice speed. Note than the rim brake model is a little lighter than the disc brake version. Unless you’re doing a lot of technical descents or wet descents, the rim brake version should work perfectly. I have both rim and disc brake models........
You might check online at R&A cycles and Excel Sports just to start looking evaluating. Good luck. There’s a lot of good stuff out there.
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