LA360 initial timing too high - are there different timing covers?

I can't see from the pix but does this engine have a choke plate on the primaries? If so and it is closed while you did this adjustment, that may explain the 19" of vacuum. Are you trying these adjustments full warmed up or cool/cold, right after start up? The engine has to be fully warmed up, and the choke plate fully open before you do this.