Can we double check that you meant to write stack 631, reach 380?
Typical stock bikes in my size would have reach dimensions around 380 and stacks about 530 or so. If your actual desired stack is 100mm - 4 whole inches - higher than that, then it seems like custom would be the better option.
And the Parlee closest to the stack/reach you gave is the medium/large size with the short top tube cap. That’s a reach of 379, and a stack of only 589 - so you’d be at 50mm of spacers to get you to 631, and typical forks may only allow 40mm of spacers.
Great links from Chad above for easily comparing geometry on different bikes. Would have 2 questions for your fitter. First would be whether they think your fit may evolve over time. A good fitter will sometimes identify strength or range of motion limiters that can be addressed and would change your optimal fit. In which case that would influence you towards choosing a bike that could accommodate likely changes. Second would be why they’ve specified a -6 stem as I would think that with your high stack numbers it might make sense to get a stem you can flip up to get some of that height without needing as many spacers.
If that’s your position and the fitter doesn’t think it will change much, I would consider a custom frame. As you say, there aren’t going to be many bikes that will get close to that stack and reach without a lot of spacers and/or flipped stem. A friend who also has high stack due to a back injury (confirmed by a very good fitter) went down the custom route a few years ago and loves his new bike. Only issue is how substandard all other bikes feel in comparison, so his other 2 bikes rarely get used and he hates hiring bikes (we go on bike trips abroad every year). Guess it’s a good problem to have though!
Just looked it up as I wasn’t familiar with the Chebacco, seems they do a Short, Mid and Tall option in each size which is likely why the fitter recommended it. So going Large and Tall would give reach of 385 and stack of 628 which is pretty close.
This seems like a relatively upright/endurance fit…I wonder why they recommended a negative rise stem? Flipping it to +6 gives you 20mm more effective stack (and shortens the reach a bit). As @Weiwentg mentioned, a 58 cm Trek Domane could be a good fit with spacers or positive rise stem.
The Domane is the first bike that came to my mind as well. The stack and reach are definitely in the more comfortable range, and the rest of the geo (slack HTA and low BB) matches that type of riding style really well. It also clears at least a 40mm tire!
I’d go for the 60cm and find out what reach you need in your handlebars. I’ve seen everything from 75 (common these days) to 95mm, which affects your overall reach considerably.
If you want to do gravel too, I’d look at the Domane or new Roubaix because they’ll take 38 or 40mm tires. The Endurace has a max of 35mm and the integrated cockpit may be a challenge to dial in your fit.
You could go with either size! I like to size up for endurance bikes, though, and the 60cm meets your stack height requirements with the ability to raise your bars if you need to down the road.
With the 58cm, you won’t have that option, as you’ll need most of your headset spacers under your stem right away to get the stack you’re looking for.
The Domane is great for gravel. It’s less complex than the Roubaix and is designed really well for gravel riding. I had the last generation one and loved it! I had one set of wheels with 32s and one set with 40s.