making sunlight

Here’s what I’ve got:
photo of 70+ yr olds sitting on a motorcycle in the garage ( daytime light with garage door open) and I’m using "Recompsit" to pick a different photo as background ( of 3 guys on the road with their bikes) and I can drop the 70 yr olds’ shot in there- it all looks fine, except that the lighting for the 70 yr olds isn’t right . I’ve tried Imageready and Photoshop to adjust the lighting on the 70 yr olds photo and cannnot find a way to make that daytime light to appear as sunlight. I tried a google search first and didn’t find a find to this question: How to make a composite of a photo taken in "normal daylight" into one that one taken in sunlight?

Any pointers ?

Thanks very much.