  We present spectral density reweighting techniques adapted to the analysis of
a time series of data with a continuous range of allowed values. In a first
application we analyze action and Polyakov line data from a Monte Carlo
simulation on $L_t L^3 (L_t=2,4)$ lattices for the SU(3) deconfining phase
transition. We calculate partition function zeros, as well as maxima of the
specific heat and of the order parameter susceptibility. Details and warnings
are given concerning i) autocorrelations in computer time and ii) a reliable
extraction of partition function zeros. The finite size scaling analysis of
these data leads to precise results for the critical couplings $\beta_c$, for
the critical exponent $\nu$ and for the latent heat $\triangle s$. In both
cases ($L_t=2$ and 4), the first order nature of the transition is
substantiated.
