Wrong cluster!!! How to read...

[BMWE30]

Hey guys,
Soon after buying my 87 325, I noticed it had the wrong cluster in it. It has an "i" cluster with the 7k redline. Now...its been bugging me for awhile on how I should be reading my RPMS. I know all the other gauges are the same..but are the RPM readings on this tach correct and the red is just at the 5....or does it show the ETA tach readings, like about 1k on this "I" tach would be about 750 or so RPMs normally....how does this work? It seems screwy also cause when my auto trans shifts (about 3 on the "i" tach) the trans seems so shift okay but the rpms do not drop but 1/8 of an inch unless u let off the gas pedal. Please help me figure out whats going on here! Thanks in advance.

[Spencer]

As far as I know you only need a code plug from an eta cluster in order for it to read correctly. So even though the guage goes up to 7K the rev limiter would stop it at 5700 or whatever.

If the PO put in a diff cluster the miles might be wrong.

Spencer