The PPG of LME is about the same as base grain at 100% efficiency. 3.75 pounds of LME gives you 139 gravity points. So, if your typical efficiency is 75% (which is a good guess) your base grain extraction would be like 25 PPG. 139/25 = 5.5 pounds of Pils malt.
I'd definitely use Pilsner malt though the extract might have Vienna or Munich in it too.
Try moving the 1oz Hallertau to 60 instead of 40min but it's really hard to tell how many IBUs are in the canned stuff. If your hallertau is 4.5% alpha, you probably want to bump it to 1.5 oz @ 60 or 2oz @40min to keep it at about 25 IBU.