P-rod grip frame on 2240

I've used one one my 2400KT which is the same as a 2250, which I believe uses the same trigger group as your 2240, and yes, the P-Rod hammer is best, though there are those who have filled the "waist" of the original hammers with JB Weld to mimic a P-Rod hammer. If the P-Rod hammer is used you will have to notch it, and either fill the threaded hole of the P-Rod hammer face with a pressed pin or ground-flat set screw, or use the original threaded piece it uses to strike the valve pin.

According to this listing, it is a "go" for your 2240;
Crosman Deluxe Two Stage Adjustable Trigger System Kit 2240 2250 1377 1322 2289

P.S. I did the math on the parts in that listing, and while you can get them domestically for under $65 before shipping, you'd need to modify the bolt yourself, and the trigger group is VERY hard to find stateside... to make matters worse the European dealer who had them struggles getting the frame past Heathrow Customs. (been there... MAJOR delay)

As you can see below my only supply recourse (Europe) was considerably more expensive than North American sources given the high cost of freight. Domestic sources assured me (as of Sept 2016) that the Drop Sear Trigger Frames were not available, availability was/is subject to change. Note striker is optional, since you can plug the hammer face instead if you choose to do so. BTW the Drop Sear Trigger Frame is a COMPLETE trigger group/trigger assembly, minus the grip panels; 

• 1 piece(s)2220-1032220-103 Drop Sear Trigger Frame £49.50
•  1 piece(s)CH2009A009CH2009A009 Hammer £16.08
•  1 piece(s)1763A0361763A036 Striker £6.90