The 2N3771-2N3773 series are a more robust transistor than the 3055 and relatively inexpensive. The die in these is much larger than in most 3055's.
Expecting 300W dissipation from 4x3055 is pushing things a bit. Even with a good h/s I doubt if they'd take that. About half that is OK. Years ago I built a 30v 5a PSU with 4x3055 on individual 3C/W heatsinks, direct mounted with the h/sinks insulated, and it worked well. The temperature cutout would operate after maybe 15min if the output was shorted at max current though.
The other options are foldback current limiting, or a relay to select a lower transformer tap at low output voltages. Which is what most commercial linear PSUs do.