One trick I've used when converting from other PLCs to AB is to use SYMBOLS in the AB that matches (as close as possible) an address in the existing program.
For example, You may wish to create a data file N40:0-249 which corresponds to Modicon register 40000-40249, N41:0-250 is 40250-40500, and so on.
If you assign those addresses with the symbol of, for example, N40:0 = A40000, N40:1=A40001 and so on, then when you come to an instruction that uses the address, just type in the symbol instead of the address. RSLogix will substitute the N40 address for the symbol name, and you won't have to be looking up each address as you re-enter the code.
The example above doesn't show how handy that can be, since N40:001 is pretty clearly 40001, but when a you get a timer in the middle of the 4xxxx's, it's nice to know that T4:15.PRE corresponds to 40117, and all you need to do is type in 'A40117' in the MOV block that is setting the preset, and you'll get the T4.PRE, not N40:117. See?
If you can export your address descriptions from Modsoft/Taylor/whatever, and massage them in Excel to create a CSV for AB to import, this can speed up the process considerably, and save you from typos.