^^^ agreed.
The late factory 240 turbo auto's had a 3.91 rear end. The 240 turbo manual's used 3.73. All the non-turbo auto's had a 3.73, so your converted auto will be the same gearing as the factory 240 manual turbos. In other words, you have Volvo's choice for a manual turbo DD.
The 13c is a smaller turbo, and is better suited to a lower RPM range. Keep your eye out for a good 15G - a bit more power but still boosts well at lower RPMs. The factory '85 turbos were a T3, which is an older design, with a bit higher RPM range.
The T cam was Volvo's choice for a turbo DD cam.
You certainly want to change to a turbo cam from your NA M? cam. In a simplistic view, the intake stroke on a NA engine sucks the fuel/air mix into the cylinder. At higher RPMs, the momentum in the intake manifold helps push air into the cylinder. On a turbo engine, the boost pressure also pushes the fuel/air mix into the cylinder. With this, you need a cam with less overlap than a NA cam to avoid the boost pressure pushing the fuel/air mix straight through the cylinder and immediately out the exhaust.