777 started out as Samuel Mathers' work and was revised and expanded by Allan Bennett, so Crowley's contribution to it was fairly minor. My recommendation has always been that you make your own book of correspondences based on the sources that appeal to you, and test everything out by meditation and pathworking. That way, first, you'll know the symbolism inside and out, and second, nobody else will know exactly what symbolism you use, which can be helpful in various ways.