That opamp should be fine.
For box caps, usually sticking around 63v or under will get you a small enough cap for most pedals. The ones you listed should be swell.
The
smallest 1uf that i know of are the Panasonic film ones like these:
http://www.mouser.com/Passive-Component ... ic&FS=TrueThe 1uf of that series in 50v is just about 6mm and square. And they are nice caps.
(Actually, that link should be showing
only all of the 50v Panasonic polyester film caps that Mouser currently actually has in stock, so it can be useful for selecting other pedal making values as well)
LASTLY. If you check any of the Mouser product pages, they list the "lead spacing", which will let you know what to expect for size also. In these cases, both the ones you listed and the ones i listed show that value as 5mm. So you can actually go into the pedal and see if those electrolytic caps holes are about 5mm apart. Any of the caps listed here so far should be fine.