Dirk, I have not seen an updated pic with your new SPAL fan, but there are improvements that can be made your existing alum. shroud to help with highway cruising temps in terms of getting more CFMs through the core. Air flaps can be added to the shroud to get the extra airflow through that core. Now, your air is forced to travel through the back half with a diameter opening (16.5" or so).
SPAL can get you ( you probably need to call the tech line) their rubber flaps that are used on their twin fan shrouded assemblies that can be installed on your current shroud (need to remove shroud for this). You can also make your own with rubber material. see pics found on a site where this work was done to a 60's muscle car. The documented results in this article showed highway temps dropped 7 degrees F after the changes were implemented (flaps are just one item). They ultimately concluded the SPAL fan did not need the aluminum shroud and mounted fan directly to core. Shroud removal is a PITA of course. Shrouding air in front of rad is very important to help keep flow moving through the rad and will also help. Article link uses flexible material to seal off rad sides to accomplish this also. check this out.
http://www.highperformancepontiac.co..._radiator.html