The FINAL Wheel Backspace Thread for 1967-1969 Darts

I can't tell you for sure.... but that sounds about right.
I have a pair of factory-made centerlines that look like they were made for your exact situation. 10 1/2x15, 7 1/4 backspace, 5 on 4 pattern. They have been double drilled to 5 on 4 1/2. They are basically a 15x7 front half, 15x14 back half.

20200729_184102.jpg

20200729_184031.jpg