  We studied the variation of $e^+$ and $\bar p$ top of the atmosphere spectra
due to the parameters uncertainties of the Milky Way geometry, propagation
models and cross sections. We used the B/C data and Galprop code for the
propagation analysis. We also derived the uncertainty bands for subFe/Fe ratio,
H and He. Finally, we considered a neutralino induced component in the
antiproton flux in the mSUGRA framework. PAMELA expectations for positrons and
antiprotons are calculated. We studied in details the possibility of
disentanglement of an eventual signal component in the antiproton spectra in a
clumpy halo scenario: minimal values of clumpiness factors necessary to
disentangle the signal from the background without violating the quality of the
antiproton data fit are found. There are also given examples of total spectra
in comparison with existing experimental data and an example of PAMELA
prediction for the total spectra. The main result of this work is that for the
diffusion and convection background model PAMELA will be able to disentangle an
eventual supersymmetric signal even for small clumpiness factors.
