[Eliot Ness]

I have these caps that say .5 and 10.

The capacitor pictured is a .5 at 10 volts, but as sky noted anything over 10 volts is fine until size becomes an issue.

For electrolytic caps I usually just stock 450V for the majority of sets I work on. The newer ones are small enough to re-stuff even a lesser rated older capacitor if you're so inclined. Occasionally I'll need a higher voltage filter capacitor, but not very often. Again, as sky noted 350v is probably fine in this set, but if you have a stash that are rated a higher voltage feel free to use them if size permits.