Temps climbing in 318

I think that fan shroud isn't doing you any favors because the air is missing a big part of where the hottest coolant is.

Lets say this is your radiator.
The red represents the hottest coolant area of flow, and the blue is your fan draw area.
In spite of what people think happens in a radiator, reality is more consistant with this drawing. (you can prove it with a temp gun)

See what I mean?

That being said, flow volume is usually the cause of overheating on the hiway.
Has the block been flushed out well. (hot spots can make it overheat)
What is the age of the water pump?
Is there a spring coil in the bottom hose.

Then there is also the possibility that it is the radiator like RRR mentioned.
Was it backflushed before it went on?
How do the tubes inside that you can see look?