Buy a retro Double end MH kit withwattage to suite your needs.
Loose the glass canopy. Make a "canopy in a canopy" if you will, atatched to the lid of your cherry canopy. I would simply buy some shelving planks, coat them with poly, buy some angle bracketts, coat them with poly as well, form a skirting extending down from your cherry lid.
Mount the reflectors and bulbs directly to the cherry lid inside the newly formed skirting. MAKE SURE YOU LEAVE AROUND 1/2" space between the reflectors and the cherry lid to allow for a proper heat exchange. You dont want your cherry lid to discolor due to heat!
Next cut a hole on either side of the skirting for fans, cut some acrylic tofit the bottom of the skirting, Use small "L" brackets to hold it snug and in place and VIOLA!!! The lighting you want inside the canopy you love!!
I have personaly installed NUMEROUS units JUST LIKE THAT in brandnew aquariums for my Aquatic interiors friends down the road from me, when thier customers wantted to utelize thier beautifull cherry or oak hoods, but still have halide lighting.
It DOSE WORK. The key is the acrylic lense, GOOD FANS, and the 1/2" minimum space between the reflector and the top of the canpoy.
Hope this helps you!!!
PS:
If it hase a slotted lid simply fix a 1/4" piece of white painted, poly coated plywood over it.
PSS: Going with DOUBLE END MH will eliminate your space problems and allow you to make a smaller "Box" type skirting so it will NOT sit directly on your aquarium frame.
EDIT!!!!!!
Strike the acrylic!! Use POLYCARBONATE It is more heat resistant.