There is always the issue of when you start carbo loading before a 42 k race. Do you start 3 days before or 1 day before. Just spoke to Rujuta Diwekar, a fitness consultant and one who i highly admire and recommend to all those who want to get fit.
Rujuta says to have 3 carb meals before a 42 k. Assuming the race is on Sunday morning, then you start eating whole wheat pasta from Friday night, Saturday lunch and Saturday dinner. Ensure that you don't eat too much fat and eat the correct proportions. Keep it healthy and toss in veggies, little cheese etc.
2 of my favorite pasta recipes.
Whole wheat pasta with baby corn and brocolli :
http://99healthyindianrecipes.blogspot.com/2009/07/whole-wheat-pasta-with-baby-corn-and.html
Pesto Penne with Mushrooms :
http://99healthyindianrecipes.blogspot.com/2009/08/pesto-penne-with-mushrooms.html
For a 21k race, carb load only on the day before the race. That would be 2 pasta meals on Saturday, lunch and dinner before the Sunday morning run.
Happy running.