Not having a Graphic and a 300 Symmar in front of me, I cannot be certain - but I sincerely doubt you'd get that lens on the front standard of a speed, even with adapters. Plus, the bellows are too short.
I'd get the 300 Symmar, if you want a longer- but not really long lens - get a 420, 16 1/2" Artars are fairly reasonably priced but will not give you tons of movement on 8x10.I use one for portraits and such on 8x10. The Symmar will give you all the movements you're likely to need (for general use) on 8x10.
As for Dagors, they cover quite a bit if you are contact printing - their legendary coverage is just that, a legend; if you are enlarging negatives they are a 70 degree lens just like the Symmars. A 12" Dagor is small and light, a 300 Symmar is big and heavy - and a 360 Symmar is a monster. The Deardorff V8 is lovely to use, very intuitive.
I don't think the Graflex has the bellows for it either. My Crown has some pretty serious bellows extension going on with just my 210 Symmar.