Most stock amps are quasi-complementary output. We rebuild them full-complementary with White Oak Audio kits and parts.
The newest greatest outputs are available there.
Here's a link. https://www.whiteoakaudio.com/
Start reading the WOPL (White Oak Phase Linear) Building threads and study the photos.
Read, read, and study the photos. Very few of us resurrect old amps. Most get rebuilt with all new parts except for the transformer and perhaps mechanical meters, or chassis and faceplate. Although Joe (aka "Geppeto", the owner of White Oak and a member here) also offers new superior chassis and faceplates.
About 40 years...
You may not be able to HEAR the difference, but the benefits of increased Safe Operating Area and other specs make the purchase of these devices a no-brainer, as Lee said above. And, they are not even expensive.
The ONSEMI MJ21195/MJ21196 output transistors are far superior to what we see on the back of these Phase Linear amplifiers. They were good in the 1970's and 1980's, not today.