RE: Speedometer off by 10mph, what could it be?
 

Can't find anything on this number.

There may a steel serial number plate riveted to the trans body, look on top of the diff housing.

You should be able to see it by looking down between the distributor cap and resontator box (the box is connected to and below the air intake tube going to the throttle body).

RE: Speedometer off by 10mph, what could it be?
 

WELL I think I know now what is causing this issue.

I bought the car about a month and a half ago from a nice lady in her 50's

the cluster says 137,000 on it

the carfax says it had 296,000 in 2004 so I think you know what happened, they did a roll back on it, and in the process, probably wrecked it.

also I had the car up for sale, I wanted to buy a motorcycle, and a guy called me and said he too looked at this same car when it was for sale last time, and he noticed a sticker on the timing belt cover that said 234,000 miles. conveniently , that was removed before I bought it.