Slight changes to Harvard's agsm.bst [closed]

Question

I've been writing my thesis and using bibtex, unfortunately I could not find a .bst to match the required format. It requires some particles to change from English to Spanish, as well as some changes in formatting. The most similar style I could find was Harvard's agsm.

1. Authors to be listed with "y" instead of "and".
2. Use "et al" in text when there are more than 3 authors.
3. Underline the title.
4. Place the year after the title.

This is shown here!

Can this please be done by modifying directly the agsm.bst? I've tried to use makebst but latex doesn't seem to be able to use the .bst produced by that.

My code is this:

\documentclass[10pt,oneside,letterpaper,spanish]{book}
\usepackage[utf8x]{inputenc}
\usepackage[activeacute,spanish]{babel}
\addto\shorthandsspanish{\spanishdeactivate{~<>.}}
\decimalpoint %\spanishdecimal{.}

\usepackage[spanish]{babel}
\usepackage[dcucite]{harvard}

\begin{document}
asdasd \cite{chsh_inequality} asdasd \cite{aspect_test_bell}
\bibliographystyle{agsm}
\bibliography{ejem_biblio}

\end{document}

and my bib is

@ARTICLE{chsh_inequality,
   author = {{Clauser}, J.~F. and {Horne}, M.~A. and {Shimony}, A. and {Holt}, R.~A.
    },
    title = "{Proposed Experiment to Test Local Hidden-Variable Theories}",
  journal = {Physical Review Letters},
     year = 1969,
    month = oct,
   volume = 23,
    pages = {880-884},
      doi = {10.1103/PhysRevLett.23.880},
   adsurl = {http://adsabs.harvard.edu/abs/1969PhRvL..23..880C},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}

@ARTICLE{aspect_test_bell,
   author = {{Aspect}, A. and {Grangier}, P. and {Roger}, G.},
    title = "{Experimental Tests of Realistic Local Theories via Bell's Theorem}",
  journal = {Physical Review Letters},
 keywords = {Fluorescence, phosphorescence},
     year = 1981,
    month = aug,
   volume = 47,
    pages = {460-463},
      doi = {10.1103/PhysRevLett.47.460},
   adsurl = {http://adsabs.harvard.edu/abs/1981PhRvL..47..460A},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}