To be fair mate, if its come this far, like 20 years without ever having been touched, thats done fucking well.
Obviously its a hard choice, BUT, the way i see it, if i walked up to it in a car show, and saw what you described as the towing eye cover being a different colour to the valance, my first reaction would be, "oh dear look at that poor colour match, its obviously had some spray work in its past"
You know its original......but i doubt many people would see it that way.
I'm not 100% but im sure all the bits for the bumpers are sprayed seperately then put together.....? Cracking would suggest they have been re-sprayed without being taken apart?
And the other problem you have, the whole car is going to of faded over time, you can guarantee the bits you have sprayed will look far superior to the rest of the car then?
Maybe a whole re-spray?