I make this with rhubarb all the time, and it is delicious and easy.http://www.food.com/recipe/grammie-millers-swedish-apple-pie-84441
For the change to rhubarb I use 8 cups of one inch rhubarb pieces for the whole recipe - 4 cups for each pie plate if I'm doing it in the two smaller dishes. Before putting the rhubarb in the dish [or dishes] I mix it up in a bowl with extra flour and sugar. Here are the proportions:
9 x 13 pan 9 inch pie plate
8 cups rhubarb 4 cups rhubarb
1/3 c flour 2 1/2 T flour
1 to 1/14 c sugar 1/2 c sugar, rounded
I compared standard apple and rhubarb pie recipes to decide how much sugar and flour to add to the rhubarb in the bowl. This could certainly be adjusted to someone else's taste.