A few things i remember about the movie. Rock climbers and gymnasts made up the team of thieves. One scene had to cliffhang across the roof and old man has a heart attack and dies. One of the last scenes, one of the thieves holds both jewels in each hand and he starts breathing fire, but after a lil bit he is back to normal. I also believe there is a scene where a snake comes out of a hole and bites one of the thieves in the face.
Sounds like it could be “Treasure of the Four Crowns” but that was from 1983.
http://www.imdb.com/title/tt0084781/?ref_=fn_al_tt_1