Well I'm assuming this is for a S30, because that is the information I'll be providing.
'75 280z
49-1/2" side to side
12-1/2"to 13" from windshield to face @ center of dash.
10" from left side to c/of steering column
7" from top of dash to opening of steering column (top of clamshell)
12-1/2"to 13" top of dash to bottom @ the center of dash