I had thought I had posted a reply to your alu wheel questions. I have four sets actually, one on the 73 they came on, another set off a mustang, a set off a Mercury and a set off a Maverick. I saw one reply saying that the Maverick ones were smaller. I just went to the barn and pulled out one off the mustang, maverick and the Mercury. There are three different diameters but the Maverick and Mustang were the same about 2.440" calipers would not go into wheel to get accurate, The other two sets one had 2.75" dia. and the last was 2.84" dia.. They all had the same offset and measured from bead to bead 6" and over the wheel 7". I took some pics but cannot get them off the new camera do not have the software.
If there is another diameter I do not have them but I know one set was off a Maverick I still have the center caps. I know the Mercury is larger than the Mustang due to the front hubs and rear axles having a larger diameter that centers the wheel and supports the car weight the lugs just hold the wheel on and do not locate it.
Just more information. You could put any of the wheels on a lathe and open the center hole up to fit what you have.
The slots actually have the mill finish from the machine process that looks something like a 180 grit sand but for sure a mill finish.
David