Question about altering recipe for pale ale?

I want to make a pale ale, have all ingredients, but don't have a pot large though to boil 5.5 gallons like the recipe calls for. What alterations do I need to make to be able to brew in a 3 gallon pot? I already have 3 gallons of sterile water, and was planning on boiling ~2.5 gallons. Anyway, what would you do? Recipe below.

* 8 lbs. pale malt extract syrup
* 0.5 lb. carapils or dextrin-type malt
* 0.5 lb. crystal malt, 20° Lovibond
* 0.5 lb. crystal malt, 60° Lovibond
* 0.75 oz. U.S. Northern Brewer hops (5.25% alpha acid) for 60 min.
* 2.5 oz. Cascade whole hops (4.5% alpha acid): 0.75 oz. for 45 min., 0.75 oz. for 15 min., 1 oz. at end of boil
* 1 pt. starter of Wyeast 1056 (American ale)
* 2/3 cup corn sugar for priming


Step by Step:
Start with 5 gal. of 150° F water. Steep crushed grain for 30 min. Sparge grains with enough 170° F water to make 5.5 gal.

Heat to boiling and add extract syrup. Total boil will be 60 min. At beginning of boil, add Northern Brewer hops and boil 15 min. Add the first Cascade addition, boil 30 min., and add second Cascade addition. Boil remaining 15 min., at end of boil, add last Cascades to finish. Whirlpool and cool to 69° F to pitch starter. Oxygenate/aerate well.

Try using the Texas Two Step method. I first read about this in BYO magazine. This article is similar

Use 2 - 2 1/2 gallons in your pot. Follow the rest of your directions. Then add your sterilized water to the cooled wort and pitch your yeast.

Do you have more hops? If you want to just brew it as is, with a smaller boil, you'll need more bittering hops.

What I would do is go ahead and steep the grains in 2 gallons of water. After removing the grains, add 2 pounds of the extract and bring the total volume up to 2.5 gallons and make the beer as usual. With 15 minutes left in the boil (take the pot off of the heat) add the extract, stir well, and then put it back on the burner and finish as usual. That will get you pretty close to the full boil recipe.