Good Initial Timing and Too much Total Timing Problem. Seeking guidance to minimize total timing. 1969 Swinger 340 4 Gear

Maybe I missed it, but I didn't see where it was pinging.
57* at cruise is NOT excessive. At cruise, the engine is under the least amount of load. Some of the 57* is coming from the VA, & some/all of that amount reduces as you load the engine & vacuum drops.