RRR,
Going to add 3c worth, not 2 cents...
Firstly congrats on going to the trouble of trying MVA. 44* at idle does not surprise me [ My GTO has 48* ]. A 440 Charger engine that I set up a few weeks back idles with 42*. Could be a few reasons for that high amount. Poor chamber, lack of quench, low compression, low vacuum [ cam ] etc.
You really need an adj VA unit. Even if it means getting a different dist; Allen Key needs to be fully CW [ softest spring setting ].
The #1 cause of comments like post #7 is bad set up leading to erratic/varying timing at idle.
To anybody setting up MVA: before closing the tool box, always check the timing at idle, in gear if auto. If it is unsteady, you need to find out why because it will cause problems.
