The Model T is not 300 watts. It's more like 150. Can be used for guitar or bass.
There were essentially three eras of Sunns. The first era, the Sundholm period, had a lot of different models, all tube, IIRC based on Dynaco circuits.
Examples of these heads would be the 200S and 2000S. There were lots of others, but they tended to be somewhat similar, fairly minimal EQ, differing amounts of power with the 2000S topping out at a very conservative 120 watts (later boosted to 150 and renamed the 350B).
The second era of Sunn was the Hartzell era. The Model T was produced during this era, as mentioned previously. The solid state Sunns (Concert Bass, Coliseum, etc.) were also mainly built during this era.
The last era of Sunn was when they were acquired by Fender. The most notable products of this era were a redesigned Model T for guitar (though I suppose its clean channel might be usable for bass), and the 300T (300 watt tube bass amp). The preamp section of the 300T was also used in the new 1200s, a hybrid head (solid state power section, tube pre section... also, no relation to the Sundholm era 1200S, which was a guitar amp similar to the 2000S).
After that, they were discontinued. The Sunn 300T, however, is still widely available as the Fender Bassman 300Pro.
It should be noted that all three eras featured substantially different designs from one another. The Fender era bears little in common to the Hartzell era, which in turn was quite different from the Sundholm era.
