Grapevine, LakeWorth, Eagle Mountain, Ray Hubbard, all hold large Carp. Also I'm a firm believer the Trinity River holds some large Carp in it as well. Fishing for large Carp is similar to fishing for large Flat Head Catfish. You have to put in the time, research, etc. What I would do is pick a spot closest to your home, stick with it and fish it, chum it, etc, etc, for days, weeks, etc, and eventually you should start catching larger fish. One tip that has worked well for me over the years is to fish PAST my chum line. Seems like the bigger fish are always watching the smaller/younger ones getting hooked.
lol..