1986F150Six wrote
An unloaded engine, whether @ idle or at cruise conditions can tolerate quite a bit of advance.
In my previous studying, I came across a write-up that claimed many SBF's ran as much as 45 degrees advance while cruising (at low load). That's initial, plus some centrifugal, plus vacuum advance.
1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995