ET23 is common on wheel for the W123 cars.

Factory alloy wheels are 6" wide at ET30. Your wheels at 7.5" and ET23 compares as follows:

7.5" - 6.0" = 1.5" different in width or 38.1mm.

38.1mm / 2 = how much inward and outward the edges would be compared to stock. 19.05mm

ET30 - ET23 = 7mm

That means your Einspresstiefe (ET) or "pushed in depth" in English is 7mm further inward. This means the outer edge is 26.05mm further than stock (19.05mm + 7.00mm). The inner edge will be 12.05mm (19.05mm - 7.00mm). 

It should fine from the inside. However, you are going to have some tire peeking out of your arches. You don't need spacers. You need really narrow tires! My preference is stay under 7" up front. The rears are more forgiving because the rear track is about an inch narrower. You just need to make sure you clear the slider.

Regards,

BenT
sent from my electronic leash

> On Dec 5, 2015, at 1:48 PM, Aaron <a.robinson.lists@GMAIL.COM> wrote:
> 
> I confirmed they are the correct ET23 offset. I'll mount them up and try to figure out the correct spacers needed. 
> 
> Does anyone have suggestions on vendors with spacers and how to determine the correct spacer thickness?