Like the others have pointed out, that TOTAL MECHANICAL advance is WAY too big!!!

I'm a small-block guy, and with 21 initial I aim for about 35 deg. TOTAL mechanical. The VAC can is configured to toss another 15 in at cruise, and since at WOT it gets no vacum signal that keeps it safely out of contributing any advance.

Take the distributor apart and see what's going on with the advance mechanism.

It could be one of two types:
1) Old Mopar OEM thing
2) More recent (and Aftermarket only???) version which allows a much easler adjustability to BOTH the TOTAL advance as well as the actual CURVE

Here is what that distributor looks like: