You actually may be forced to move to compatible replacements if you can't find the original references.
My advise is, since it's an audio amplifier, the transistor replaced in the right/left channel should be replaced on the other channel also. It would be even better, even if it's just one transistor needed to be replaced, that you buy not only one for each channel, but a few more and try to match a pair of them with the same gain (hfe), so you wont end up with unbalanced right/left channels.
Try to put the amplifier working, first of all. Next you can play (an educated play) with different components to achieve better results.
Good luck.