All Grain from an Extract Recipe

I had this recipe I like from an extract I did but would like to try it as an all grain. How might I do it?

Here's the recipe: for a 5 gal. batch

6 lbs. Pale malt extract

2 oz. Chocolate Malt
4 oz. Crystal 40
12 oz. Crystal 80

Steep 30 min. at 150?

1.3 oz Cascade 60 min
.4 oz Willamette 15 min
.8 Cascade 0 min

Another thing is that Cascades are unavailable at my LHBS. They suggest centennial or amarillo as replacements.I plan to make a 10 gal batch. Thanks

This is converted with BeerSmith:
6.76 lb Pale Malt (2 Row) US (2.0 SRM) Grain 82.17 %
0.97 lb Caramel/Crystal Malt - 80L (80.0 SRM) Grain 11.84 %
0.32 lb Caramel/Crystal Malt - 40L (40.0 SRM) Grain 3.95 %
0.17 lb Chocolate Malt (350.0 SRM) Grain 2.05 %
Now for the hop subsitutions check out:
http://byo.com/referenceguide/hops/

I would just keep the specialty grains the same, and use 2-row for the 6 pounds of LME. Assuming a 70% efficiency, I'd just use 9 pounds of malt for the extract.

For hopping, did you do a full boil with the extract? You might have to adjust the hops if you didn't, if you want to duplicate the same IBUs.

I like amarillo hops, and centennial, but they are not really replacements for cascade hops. I'd bitter with the centennial and use the amarillo in place of the cascades at the end of the boil, if you can't find cascade hops.