There are distributor specs in the factory service manual. Only thing is that the manuals for free download at www.mymopar.com
do not go quite to that newness. But those older FSMs can be used as a guide, usually.
The only specs for the vac advance are related to inches of Hg, not engine rpm. You DO need vacuum advance for highway fuel economy and better drivability. On the '77 engine, there are some vacuum delay valves to modulate how the vac advance works for better exhaust emissions.
In general, the mechanical advance figures you mention seem to be "in the ballpark" for Chrysler B/RB engines. It does not seem that a big lot of improvement in power can result with more than what you now have, so I would suspect everything is good. As long as the engine does not ping on slight part-throttle acceleration for the fuel being used.
The only mechanical + vacuum advance totals were some which I saw in an Exxon Tune-Up Manual (not available to the general public, but only to Exxon station owners, which I saw back in about 1975). It used 2500rpm for a quick check to see if everything was working well. So basically, it was the mechanical advance from the factory service manual plus the maximum vac advance figures quoted in the factory service manual. These figures were usually in the 50-54 degrees BTDC range. I know, that seems a bit too high considering that we are only usually seeing mechanical advance figures at WOT only, but for a part-throttle load at highway speeds on level roads, that higher figure is good.
Usually, the mechanical and vac advance systems are looked at separately for diagnosis and checking them. The combined figures in the Exxon manual allow for a quick check of both of them as they operate together AND a quick check of such.
As the air/fuel ratio is "thinner" at that cruise situation, the mixture is harder to get ignited, so more ignition "lead" is needed so the full combustion happens when it needs to happen at or near TDC. Whereas, at WOT, the mixture is "thicker"/richer and easier to get ignited.
An inoperable or disconnected vac advance will usually result in a slightly less-responsive to throttle engine and decreased fuel economy (close to 10mpg or thereabouts) on the highway. So it is needed. All things considered, "fuel economy" needs all the help it can get.
Always look for specs for the original vehicle the engine was installed in at the factory. Unless there have been some changes to it (related to the distributor and/or carburetor), especially if the distributor is not the original one, being replaced with a more-generic-spec rebuilt item. THEN, you get to be more "on your own", using what seems to work for good performance and not pinging/detonation sounds from the engine "under throttle". But what you quote for current specs seems good, to me.
Sorry for the length,