Countrywide Financial was the top overall issuer of mortgage securities during the first quarter of 2005, easily outdistancing its closest competitors in the primary and secondary mortgage markets, according to a new ranking and analysis by Inside MBS & ABS. The California-based company issued a total of $66.53 billion of MBS during the first quarter of this year, or 15.4 percent of total production for the period. Reflecting the overall shift in the market away…