Overheating -- Corrective measure questions.

One thing I see that kinda jumps out is, you've introduced too much fan into the shroud. Generally, you're supposed to have about half the fan out of the shroud, maybe a little more. Yours is the opposite. Most of the fan is in the shroud. I would try a shorter spacer. You have the room from what it looks like to back the fan out some.

The second thing I'd recommend is a Stewart high flow 160 thermostat. Getting as much flow as early as possible will help the engine from ever getting to "that point".

I like that fan. Although it's not the five blade staggered fan, it is staggered. The MP engine book "says" the five blade staggered fan moves more air, but I don't know if it moves more than THAT fan. If it does, it's splittin hairs. I think backing the fan off some and the cooler high flow thermostat will get it. Make sire it's a Stewart. They ain't cheap, but they're worth the extra money.