it won't move....

Yes doing something wrong installing a shift kit can cause no drive. But let me ask you this. You say it's an older cable shift trans, right? If so what year is the torque converter for? Your transmission uses an 18 spline converter. They used 18 spline converters up to 1967 then in 68 went to a 27 spline converter. If you bought a converter for a newer trans it'll slide right in but won't engage into the input shaft so it'll act just like it's not hooked up.

That also may be why it's leaking like it is.