Hello from USA.
Thanks for the update.
Yes, a 4AGE can mount in the engine bay of an E70.
You have several ways to go.
You can tune up and add some performance parts to your 4K. You could easily get 50% more power out of that engine relatively cheap.
The 4K does have much in common with the 4A and 4AG series motors. You can fairly easily mount a 4A or 4AG in to the engine bay. Please keep in mind that the 4K is carbureted and the 4AG is fuel injected. You might be able to find an intake and carb for a 4AG, but why? You will also need to find a wiring harness for the 4AG.
You might also consider a 2T-G. That engine is DOHC and was an option in your car. The 2T-G has 55% more power than the 4K.
You also may find more fun and satisfaction in hopping up the 4K. You'll spend less money and take pride in your own work.
en.wikipedia.org