And just when I started to reinstall the front axle I found a little rust bubble in the drivers side wheel well where the engine crossmember attaches. So I decided to scrub both front wheel wells back to bare metal and cure them. 2 small rust spots on the drivers side and another one on the passenger side were welded. (Thanks Pentti)
Then I applied some rust converter on the complete area, primered and painted it with Brantho Korrux, applied some transparent undercoating and sprayed some waxoil in the cavities of the front frame.
Front and rear axle parts are now back on the car. Still have so many little things to do before the car will be off from the jackstands. This week I'll finish the interior. Passenger bucket seat, Radio block off plate,... and I'll change the brake fluid, coolant, oil&filters,...
Next week I'll hopefully get my wheels back from painting so I'll be able to get the car on the lift and do a basic geometry