Hello Thales,
great start.
I would like to also point you to this:
https://www.therpf.com/showthread.php?t=283935
or alternatively his facebook site
https://www.facebook.com/Alien-Narci...0214174234114/
This guy did a whole detailed CG model based on photomatched images of original model. He will not release 3D model, but if you ask him he coud do some ortographical renderings for you. That would make invaluable and most precise reference you can get.
Reference photos of original model on his FB page:
https://www.facebook.com/pg/Alien-Na...39045273351004