Helpful thread with part #'s if you want the mrod trigger for your Discovery.

[0351_Vet]

http://www.gatewaytoairguns.org/GTA/index.php/topic,35722.0/topicseen.html

To order the parts call Crosman and ask for their parts dept. 1-800-724-7486
For the challenger stroke adjustment assy, mrod trigger assy & guard you will be required to give them the part #'s:
Mrod trigger assy # 1763A105
Mrod stock assy # 1763-103(no trigger guard # available since they come with stock, so ask for guard from warranty dept so you don't have to buy the stock with it)
Challenger stroke adjustment # CH2009-110
Challenger/PRod hammer assy # CH2009-120(buying elsewhere, price unknown at this point)

Total from Crosman was $81 shipped.

Great thread over on GTA......       

[1377x]

we have that info floating around here also
no prices because they change