Effective Domain Masking (and WordPress)

I have many domains.

My main domain is http://www.AndrewChason.com

I am effectivly masking

http://www.meatmonkeywarfare.com

to

http://www.andrewchason.com/wordpress_meat…

Internally all my links in my WP do not show the masking; they say something like
” http://www.andrewchason.com/wordpress_meat/?page_id=3 “

But if I put something in the address bar, manualy, it goes to the right place.

Such as, it seems to know that.

http://www.andrewchason.com/wordpress_meat/wp-content/uploads/icons/test003.jpg

is the same as

http://www.meatmonkeywarfare.com/wp-content/uploads/icons/test003.jpg

———-

I have messed with the index file, and the General Options (only to screw things up, and have to undo my changes.

So, the big question, how do I get my internal page links to show the mask?

All help is appreciated.