Can't swap out axles anymore?

Not that long ago, you could take a vehicle like the D series 2wd model and swap out a different front axle, and successfully convert it to AWD/4wd. Now, you can't do that anymore unless I'm missing something. I've tried to swap out for a different front axle option but it remains 2wd?

Also, apart from breaking it is it possible to remove the front axle(s) from a FWD/AWD car (ie: 80s Pessima, Sunburst)?

 

Check the transmission part click '>' and you will see the transfer case and the you must change to 4wd Hi/Lo transfer case to make the 4wd system.