Anyone know the specs on these wheels? I know the sizes are 16x9 and 16x10, trying to figure out what the offsets are. Any help would be highly appreciated.

 

I'll post a good site later that will help you figure it out easily.

This one might help also: http://www.1010tires.com/WheelOffsetCalculator.asp

 

Here's the second site:

https://www.rsracing.com/tech-wheel.html

Site seemed to be down and I could not get in earlier. Sorry.

 

If they are 9x16 front and 10x16 rear there was only a couple cars in that era that they would have worked on. From the looks it was likely made for a 5-lug 88-89 Testarossa. from memory the fronts were about 45mm and the rears about 60mm. Measure the wheels from outside to outside to get overall wheel width. Measure backspacing of wheel from extreme inner edge (use a straight edge) to flat part of back pad (the part that touches the brake hat on the car). Subrtact half of the overall wheel width from the backspacing measurement, multiply the result x 25.4 to convert to millimeters.