New commercial mount for 2004R transmission
Treblig is right, the angle is what's important.
Yes, that angle will roughly translate into the distance from the top of the tunnel to the output shaft of the transmission, but here's the problem with that- too many variables go into that distance. The distance from the output shaft to the top of the trans tunnel will change from car to car, because the trans tunnels weren't a critical part. Meaning the tolerances could easily be a 1/4" to 1/2" different from car to car. The torsion bar crossmember has to be pretty close, but the floor isn't always tight to that crossmember, they were only tacked down in a few spots. Not only that, but the height of the engine isn't exactly the same on all of these cars. Depends on how worn out your engine mounts are, whether they're the biscuit or spool type mounts, whether you're running rubber or poly mounts, etc. So, if all you do is match the measurement from another car there's no guarantee that the transmission angle will be the same/right, even if the distance to the tunnel is.
The angle is the measurement that has to be right. The distance shouldn't vary a whole lot, but it isn't the critical measurement, the angle is.