I want to make a book which has the following specifications for margins for odd and even pages.

How I can do this in letter paper?
This uses geometry to define the paper and set the average margins of each page. Then, the horizontal margins are offset for even and odd pages to get from the average to the target margin. For the vertical margins, I used Heiko's answer at Shift Odd Page in Duplex Print to shift the margin downward on odd pages.
\documentclass[twoside]{article}
% DEFINE PAPER
\usepackage[letterpaper, portrait]{geometry}
\usepackage{lipsum}
%SET AVERAGE MARGIN
\geometry{
left={3.25cm},
right={3.25cm},
top={3.5cm},
bottom={3cm},
}
%SHIFT HORIZONTAL MARGIN ON EVEN/ODD PAGES
\addtolength\oddsidemargin {0.75cm}
\addtolength\evensidemargin {-1.25cm}
%SHIFT VERTICAL MARGIN ON ODD PAGES, BASED ON HEIKO'S ANSWER:
%https://tex.stackexchange.com/questions/79688/shift-odd-page-in-duplex-print/79708#79708
\usepackage{atbegshi}
\AtBeginShipout{%
\ifodd\value{page}%
\edef\mytemp{%
\ht\AtBeginShipoutBox=\the\ht\AtBeginShipoutBox\relax
\dp\AtBeginShipoutBox=\the\dp\AtBeginShipoutBox\relax
}%
\sbox\AtBeginShipoutBox{%
\raisebox{-0.5cm}{\usebox\AtBeginShipoutBox}%
}%
\mytemp
\fi
}
\begin{document}
\lipsum[1-20]
\end{document}
\setlength\oddsidemargin {0.03in}\setlength\evensidemargin {-0.03in}– Steven B. Segletes Jan 15 '14 at 17:25\oddsidemarginand\evensidemarginallow one to do... they shift the text on the page; they do not grow both margins by the specified amount. – Steven B. Segletes Jan 15 '14 at 18:48book, the odd/even pages are already off-center if[twoside](the default) is used.amsbook, on the other hand, defaults to[twoside]but centers the page content so that the software used to create offset plates for the printing press has a uniform and reliable "origin" to place the material accurately on the plate; on the printed (and bound) pages, however, the asymmetry is obvious. – barbara beeton Jan 15 '14 at 19:05