800 would be Ok but hard acceleration it can be another 100. The picture below shows 800 post and 1300 pre.
The biggest problem you have is the lag time between the gauge readings. Post is very slow to react to the actual temperature the pistons are seeing.
1250F is the melting point of aluminum (pistons).
The closer the probe is to the pistons the better IMHO

 

Well, so much for that weekend project. Going to have to wait till Monday to pick up the extra parts. Thankfully it appears there is enough wire to reach down to the manifold.

 

I'm with jim on this one.

Even if the gauge is "scaled" for the post turbo setup, who's to say its correct?