I know we use the rear axle from the 4th gen but is it possible to swap the entire k-member and suspension as a cc complete package from a 4th gen into the 3rd gen chassis?

 

NO
Anything is possible with a saw and a welder

 

and a little pain, dont forget pain.

 

 

As far as anything even remotely resembling a bolt-up, NO. The entire front suspension is different, a completely different design, and consequently everything that supports the one is incompatible with the other.

Well, almost... but even so, some things are much more likely (less unlikely?) than others.

 

Bolt-on? No, not even close.

Fabbed in? How much cutting/welding/machining/finishing do you want to do?

If you turned the chassis into a tube-frame thing, you could fit a 100% custom race suspension under the skin with all the bells and whistles.