All HX Sandmans had the single headlight front from the factory.... The BO6 Ambulance pack is sometimes mistaken for a Sandman as they came with GTS dash, bucket seats, Premier trim and the twin headlight front.

I have welded in a panel to fill in a sunroof hole on a mates XY Fairmont many years ago and it is extremely difficult to do without warping.... unless you are very competent at welding I wouldn't suggest attempting it.

These days there are excellent panel glues available and can be used quite successfully by the amatuer restorer. I would cut the roof section needed from a van being wrecked to use as the infill panel, the edge around the hole is recessed using a special tool, your infill panel is cut to size and then glued in. Once the glue has set you bog the joint and prep for paint. Fortunately the joint on the inside is covered by the hoodlining.