I assume you are responding to Dr. Cordain's book. I don't have my book here but as I recall there's a chart in the book on the GCI of foods.

Low to moderate I believe would be a yam or other root vegetables. I think certain fruits, like berries, are mentioned in the book. I believe the book also mentions protein shakes.

High GI carb would be a banana or apple.

Stage III I would say yes, eat your typical Paleo meal.

For Stage IV I do not believe that he's saying you should eat those things. I think he's saying you can eat nonoptimal things. I choose to still keep those things out of my diet for many of the reasons explained in Robb Wolf's book.

To your last question, I don't think you would change your eating just because you train at night. The only difference is your post-workout meal might also be your Stage IV meal if it's your last in the night.

GI in relation to athletic training is meaningless especially in the context of paleo; a high sugar fruit has sugar, fructose and glucose as well as minerals such as potassium which aid in blood sugar control. I don't know of any carbohydrate rich food that would be all that high unless it has been treated in someway, probably to the detriment of other nutritional factors.

Whole food sources of carbohydrates such as tubers, fruit, rice etc are all good for supplying the glycogen depleted body. There is a, personal, variable amount of carbohydrate that's optimal, trial and error for me showed that around 200g any time, before during or after is about right for me (BW 100kg). Though to get 200g in often requires fruit juice, sugary coffee and milk which doesn't neatly fit the paleo framework.

I run ultra distances and I loosely follow the Paleo for Athletes book (although from what I've read, I am probably mostly Peatarian). I maintain a very healthy BMI on about 3000 calories a day and about 300g of those are carbs (I know all of those things make people on here cringe, but it works for me). I use the following for my carbs: lots of fruit - mostly berries but also watermelon, cantaloupe; sweet potatoes and other squashes; greek yogurt or homemade yogurt if I have time; and Haagen-Dazs.

New 'baby ' potatoes boiled with a little bit of salt make EXCELLENT training food! Throw them in a ziplock and you have carbs and sodium in a 'paleo' approved way :) I know a lot Of athletes who use this trick who aren't paleo buy prefer whole foods over gels and sports drinks.

Make a fruit smoothie for post workout blending berries, oranges etc for your carbs post workout and for protein hard boiled eggs, turkey breasts or fish. Mix it up at the end of the day carbs are carbs an protein is protein the body will break it all down the same way if I'm not mistaken, for example sweeteners in drinks are seen as sugar web they are digested. Trail an error I guess my friend