Upto my knowledge, I can let you know the difference in IOS commands use.
Cisco IOS Software, 3600 Software (C3640-IO3-M), Version 12.4(1a) has the following commands with it.
ip inspect tcp idle-time 60
ip inspect name screen_in ftp
ip inspect name screen_out ftp
Version 12.3(11)T5 has the following commands with it.
no ftp-server write-enable. The above three commands may nto be available with 12.3(11)T5.