Kokomo is mostly ex Pennsy and NKP tracks that are now shortlines with one still operated by NS. I have heard there is a plan afoot by the city to sever one of the lines that goes through the heart of the city.
Gas City is where the ex-Pennsy Panhandle line and the ex-NYC Marion branch come to within a few blocks of each other for the run to Marion, In where they cross without a diamond. The Panhandle Line, a former double-track line is now just a branch line that goes only as far as Redkey and sees only locals. Across the river from Gas City is Jonesville where you can walk the former C&O line on the Cardinal Greenway. The Marion Branch is a little busier now than when Conrail ran it. Several trains from Cincinatti turn at Muncie and Alexandria to get to the big yard in Elkhart. Gas City sees trains like 144/143 175/176/ 311 and several locals and grain extras.
Your best bet for trains is in Muncie where the ex-NYC nee Big Four Cleveland-Indy-StLouis B-Line (double track) crosses the busier NS New Castle District Fort Wayne-Cincy line. The diamond is just south of downtown near Walnut Street. You can drive in circles around the diamond and see the approach signals for three directions easily. Both lines see in excess of 20 each daily. As a bonus NS runs one Triple Crown roadrailer southbound late morning/early afternoon except Monday and northbound early/late evening. Look for 6th street south of the diamond. This is where the trains going onto the Frankfort District peal off of the New Castle District to go West. The area isn't the greatest, but I've never had any problems sitting in the parking lots of the factories adjacent to the tracks.
Do you have a scanner? If so, 160.44 covers NS in Logan and Muncie. While in Logansport listen to 160.38 for trains coming into the crew change point of Peru, just a few miles east of Logansporton the busy ex-Wabash. The Marion Branch was recently switch from a dispatcher in Dearborn Michigan to one in Fort Wayne. I think they use 160.44 now also (actually the same dispatcher as the New Castle District). Listen to 161.07 for trains on the Redkey Secondary, one a day, maybe. Since the B-Line is former Conrail territory dispatched from Indy, CSX uses 160.800 most of the time.