Two packages with different version, from the same source

["Nelson A. de Oliveira" <naoliv@gmail.com>]

Hi mentors!

I have a doubt.

I am creating a package of a Firefox/Mozilla extension. Upstream
author reselases two .xpi files, one for Firefox and another for
Mozilla. Since they are small, I was wanting to create just one source
package (including both .xpi files) and generate two binary packages
(one package  for Firefox and the other for Mozilla).

The problem is that upsteram author released a new version of the .xpi
just for Firefox.
The extension for Firefox is on version 1.4 and of Mozilla is on version 1.3.2

What is the best solution for my problem?
Put both .xpi files on the same .orig.tar.gz and create two binary
packages, using dh_gencontrol with the -v flag? If I make this and,
for example, he releases version 1.4 of Mozilla extension, both
packages will be regenerated? Will I have to increment the Firefox
package's version? (I am really confused about this solution).

Or do I create two source packages?
But the two source packages will be small (any problem on this?)

Or maybe another better solution?

If someone could give me some hint about this problem... it's making
me very confused... :-)

Thank you very much!

Nelson