I am almost ready to buy spacers for the Gen 4 5 spoke rims that I purchased for my 89 Firebird. I found these and according to the site they are supposed to fit. They are marked 2"5x4.75 with a 70.5mm Hub bore. During my research I found that the center bore on our hubs is actually 70.3mm. My question is this.. Would that .2mm (two tenths of a mm) cause this to be the wrong part (not fit) or is that some kind of universal bore size that will just be closer to snug? Im kinda new to this, so any insight here to prevent me from picking up the wrong piece would be helpful.

This is what the rims look like 16x8


Thanks for shedding light on this subject.

 

The lugs will center the adapter so the inner bore is not that critical

 

A quick update on the situation with those adapters. I ordered them and quickly (they paid for a 3 day rush) received them. I eagerly went outside to put them on. The hub centering rings are a tight fit on the stock fire bird rims on the back wheels. I put the adapter on the front and was shocked when it lacked a quarter of an inch from laying flat against the hub. Further inspection determined that the ID of the hub centric portion of the adapter was actually 1/8th of an inch too small. Weighing out the options, I decided not to send them back but instead route the inside of the adapter with a sanding drum. A few hours later I slipped the adapters onto the hub, torqued them down and was able to bolt on my gen4 wheels.
This whole operation ended up taking a bit more time than I would have liked, but the wheels fit and are running true as well. Ill be ready to retorque after a few more miles and will follow up every couple of days for a few weeks.
Having said that, were I to commit to doing this again even knowing that this piece didn't fit right out of the box, I would certainly do it again. Thanks for your help.