I think that you've effectively answered your own question. You've fixed the bayonet. Why? - because it was was butchered and now it's fixed. Or it WILL be when you get it correctly blackened again. So what on earth would possess you to leave a set of old manky grips on it? So fix the grips too! Don't even bother using those modern repops. Just go out and find yourself a bit of old gnarled walnut and carefully make yourself another set that fit and slightly overlap the edges.
I'm of the old-time real Armourers school where what comes in the place only goes out perfect. Just like that bayonet would. It has absolutely no historical significance whatsoever, rare and valuable like that, it ain't - and those tatty old grips should be in the bin.
I hope others offer other opinions.