The problem I see with many of the terminal boards is often times I suspect they had been refurbished over the years... switches replaced and so on. It's not break in at all either... as I have NIB vintage G80 models with super smooth vintage blacks. In case of Cherry it's all about getting boards made before 1991, but before 1988 is even better. G80-1000HA* models would be an excellent chance, and any G80-0*** MX model pretty much a guarantee even though I feel dismantling them is a terrible thing to do. Other boards like those made by Dah Yang (Unitek, Magitronic, Dytcom, etc) most often have blacks, but you may find blues as well. Very old Qtronix may be an option if you see them for cheap... but again they could have blues or high chance some kind of MX clones...
Or if you want something a little different, hunt down one of the old TA typewriters that have the MX linear white/clear switches. Personally these are my favorites, but I haven't had a lot of luck getting more of them to fill up full keyboards larger than 60%.