Trumpeter 1/32 MiG-21 F-13 and Trumpeter 1/32 Chinese F-7 II kit differences ??

Hello, Info needed. What are the differences (in kit parts, sprues ...) between the following Trumpeter 1/32 kits:

Of course, decals are different. But how about plastic, fuselage parts, wings, armament ... ? As I have achance to get F7 kit at half the price of MiG-21 F-13 kit, could I use F7 kit with appropriate decals to make MiG-21 F-13 ??

Thanks, Zac