I have an idea, you can use four pair power trs. MJL1302A/MJL3281A (15A 200V 200W) per amp channel and fixed the power trs. on both heatsink sides as the thermo sensor placed.
Yep, I had briefly considered squeezing some more parts on the heatsink, and I'm sure someone skilled could make it work, but I have decided to just do a simple rebuild using replacement devices. Thanks for the idea!