Most important would maybe be the voltage from the power supply. I put 2 powerful and nice sounding class D modules in my Denon Poa 1500. They fit the 70 volts perfectly. Cheers! I sold the one working original module for 100 dollars.
If your tech is able to reproduce an amplifier circuit board they should be able to answer all your questions as well.
Do you have the link for those boards ?
I don’t know the price yet from the tech .
Is there a kit available of output boards that will fit in the amp ?
It depends on your voltage. Mine were LJM D25 I think, but they are old designs. Maybe you want something based on newer chip. They were assembled, so almost plug and play. I didnt put ekstra speaker protection. Maybe I ought to. I bought on AliExpress. Maybe 40 dollars each.
Well I opened the amp and is missing the power supply too, can I even get a power supply for the amp ?
For once I'm going to get ahead of @nigelwright7557 😁 and advise you of the EBB modules which are straight derived from the Maplin module and to find a power transformer to put in your pretty box.
https://www.ebay.fr/itm/121457218844
https://www.ebay.fr/itm/121457218844
I really like the idea, are there more modules like that but with 4 output transistor per board ?