17x10 is really too wide to due without them sticking out.
17x8 is a good fit.
I know you can put 265 40 17 on as the max since Merk from CA has a pair. He runs a 17x8 4.75 BS and need a small spacer behind the wheel to acheive that 'perfect fit'....he also rolled rear fenders and rear drums.
I run a 255 40 17 on 17x8 4.75 with rear discs and rolled fenders.
Normally I stay away from the "will this wheel/tire fit" questions, because there's always a way to make them fit, just depends on what lengths people are willing to go to.
I will say, though, that to get a 10" wide wheel in there, you will need a custom back spacing, and even then it will be tight.
I originally tried to get 15x10's in the back of my '69 (2" wider than a '65/66). Even with 4.5" of backspacing, they stuck out over and inch from the sides of the car. They WOULD have fit if I ordered them with the custom back spacing but I got chicken. The reason ... if you order standard wheels that don't fit and don't mount tires, they'll take them back. If you order with a custom back spacing, you own them, and they won't take them back. I settled for 15x8 rims with 275/50's in back. I would still have liked to have a little more meat back there, but I can live with the 275's.