Not sure about the 1.5, but the 1.6 NA and TD cams are the same, so long as they're the same motor type (Hydraulic or Mechanical). So, you can run a 1.6NA mechanical lifter cam in a 1.6TD mechanical lifter head, and vice versa. Same for hydro.
Now, that's just going by part numbers. I've been told you can run just about any ca in any model. So, mechanical cam can be run in a hydro head.
I'm currently running a 1.9 TDI cam in my 1987 1.6NA. It works fine in terms of idling, but it seems to be light in the torque dept (high lift, short duration, vs. less lift and longer duration).
So, I guess the bottom line is, try whatever you like. I don't think it will do damage, except for changes in power, torque or economy.
Please correct me if I'm wrong out there.