Is there a way to know approximately where the altar would have been located in Solomons Temple in comparison with the present mosque?
The determination of the location of the Kodesh Hakodashim = The Holy of holies or of the altar in relation to the mosque is a complex issue based upon the rabbinical literature and the works of Yoseph ben Matityahu and also dependent upon, topographical, archeological, and historical factors. Numerous articles have been written on the subject by Rabbis and researchers. Any single answer I provide here will probably upset the more experienced in this field. I will simply say that the more popular tradition is that the rock known as the "tzachra" under the Dome of the Rock is believed to be the location of the Holy of holies. This tradition stems from the Responsa of Rabbi David ben Zimra who passed away in 1573 in Tzfat. (See one comprehensive article on this subject by Asher Grossberg in Tchumin 16, 1996)