So how am i able to make a hood for the retro-fit?
Real simple. If you want it to look nice then use real lumber vs plywood.
But what you can do to build a canopy for real cheap is to buy a sheet of 5/8" plywood. Measure the dimetnsions of the tank and make sure you include from edge to edge so the box you build will slide over the top.
Build it soyou have lets say 6" of canopy above the water surface. Put some cleats on the inside about 1" up so the canopy sits on this.
Put your lights in there. cut a door in the front if you want or put it so the top is removable. Cut out areas in the back for your hoses and equipment.
THere are some good plans and photos in the DIY forum about canopies aswell.
After you add reflectors im not sure 4 96W bulbs is gonna fit. I have only been able to get 2 reflectors in a canopy with 18" width.