Hello im new to the forums hope this is the right place to put this.
I just got a 85 camaro that use to be a v6.
The previous owner swapped in a 350 v8.
Im having a problem with the speedometer.
Its way off maybe 15 to 20 mph off.

It has a v6 cluster in it. Can i just get a v8 cluster, will that help my problem?
Or is it more technical then that?

 

Speedometer might be off due to tire size or rear end swap or the right gears need to be put in the tail housing of the transmission. You will need to pull the speedometer drive cable and driven gear out to tell what combination of gears you have.

 

Bit more involved still...Need to pull the cover off the differential and determine the rear gear ratio. Then study up on the driven gear 'sleeve' combinations. Once you know the rear gear ratio, and the existing sleeve, you can figure out if a drive/driven gear are available that will work with the existing sleeve and match the rear gear. Frequently, the sleeve and the gears will have to be changed if you've got parts like a trans from a car with 2.73 or 2.77 rear gears, and 3.23/3.42 gears like you'd find in a V6. With the wrong sleeve, the drive and driven gears won't play nicely together.

The actual cluster doesn't care if it's behind spun by a trans bolted to a V8, a V6, or anything else. The calibration in thirdgens is all drive gear, driven gear, and sleeve (or VSS on later cars).