easy, based on that recipe, just mash:
2 lbs 6-row
2 lbs flaked corn
and use 2 lbs of pilsner liquid malt extract
or, go with my cream ale PM recipe:
mash:
1 lbs flaked corn
1 lbs flaked wheat
0.5 lbs Vienna Malt
2 lbs 6-row
and use 2 lbs pilsner LME
i use fuggle and saaz in my brew.