\documentclass{minimal}
\usepackage{filecontents,pstricks-add}

\begin{filecontents*}{c_x.dat}
[67,6.5]
[3300,5.1]
[9983,3.6]
\end{filecontents*}
\begin{filecontents*}{t_x.dat}
[80,553]
[3300,600]
[9920,639]
\end{filecontents*}
\begin{document}

\begin{pspicture}(-0.5,-0.5)(12.5,10)
  \psaxes[axesstyle=frame](10,8)
  \psaxes[axesstyle=none,Oy=540,Dy=20,dy=1.333](10,0)(10,8)
  \fileplot[plotstyle=dots,dotstyle=triangle*,xunit=0.001cm]{c_x.dat}
  \readdata{\data}{t_x.dat}
  \pstScalePoints(1,0.05){}{ 540 sub } % 0.05=8cm/(120*1.333)
  \listplot[plotstyle=line,xunit=0.001cm]{\data}
\end{pspicture}

\end{document}

