Question on agent query

Hi everyone
My novel was rejected by some of the best agents and I can see why! Now I've completely re-worked it:
the plot is new
focus has changed
title changed to suit the new storyline
writing is better
some charcters have either been cut and/or developed
I've cut and rewritten chapters
the ending has changed
etc. etc. etc.

Do I mention all of the above in a query (as in, "I sent this to you before but have changed this, this this and this") , or do I query as though it's a new book? I hate to think I've blown my chances with some of the top agents, but then again, I think the new version has changed by about 60%
(I can't imagine a busy agent would even remember the original submission, but just to be on the up & up...)
Any ideas?

Great- thanks!
No one requested the rework- it was basically flat-out rejections with a couple of clues ("too much of the same thing" was how one put it.) I took this to mean IT NEEDS A *&^%#@ PLOT.

One agent sent me a form letter but had handwritten something along the lines of "not this project, but feel free to send something else" so I might circle back.

Thanks everyone! Yes, major time has passed for major revisions (over a year for some, 6+ months for others.)