in 1986, did the z28's come from the factory with the 305 tpi, posi 10 bolt rear end, and 4 wheel disc brakes?

 

sure did.

 

Sure you could order a 1986 Z28 with those options. Although most of the Z28's came with 10bolt drum brake rears and many of them didn't have positraction.

That kind of stuff is very easy to upgrade and change especially since GM made the 10bolt rear for so long and aftermarket parts are readily available.

 

what about the 145 mph speedometer?

 

Some of the early model year 1986 Z28's and IROC's got the 1985 style single pointer 85mph-max speedometer.

At some point during the 1986 model year production run GM started installing the 145mph-max speedometers and mass produced them. I'm not sure exactly when that change over occured.

Keep in mind that the govenment placed a federal mandate on cars that forced GM to install speedos that maxed out at 85mph. This is also why we have that blue line at 55mph on the speedos - this was the posted speed limit on the highway back then. The government thought that speedos that didn't go up so high and the lower speed limits was going to make people slow down and reduce the number of accidents and people that were speeding.

Some of the people that bought 1982-1984 Z28's as well as the 1985 Z28's and IROC's bought the 140mph-max speedo from GM at the dealer. These units have "Z28" on the face of the speedometer.

1986 was also the first time you could order fog lights on a Z28 aswell. 1985 was the first year of the updated nose and ground effects package. In 1985 the only camaros that got fog lights were the IROC's.