That looks like the AnTek version, I buy my Toroidal transformers from him, like the one in the rear of the picture.
Linear has come to be the description for any transformer-bridge-capacitor supply, but technically it would normally have a series pass transistor or? for linearly (non-digital/switching) control of the DC output.
The tailoring of Toroidal transformers is fairly easy, you have to know the turns/volt to know how many turns to take off, say you wanted to reduce a winding by 10v output and the transformer had 2turns/volt, then removing 20 turns would do it, turns can also be added to increase the output also. Or you can add a completely separate winding, as long as you do not exceed the total VA of the transformer.
If you want to find out exactly before hand, then wind on a small conductor of 10 turns and measure the AC, the math can then be done.