Is there a dictionary for pronunciation explanations?

All dictionaries I have seen that state vowel quantities simply state them but do not explain how the quantity of each vowel was determined.
The same goes for the distinctions between vocalic and consonantal I/J and U/V.
Is there a dictionary which explains how the pronunciation is known?
I suppose it would be an etymological dictionary of sorts.

For example, a dictionary might tell me that a perfect form of velle is voluī.
But how do we know that it is not volvī or vōluī?
(Please don’t answer this specific question. I am looking for a resource where answers like this could be found.)
The explanations could be, for example, citations of specific verses where scansion indicates the pronunciation.

I recently answered a question about the pronunciation of quoniam.
Lewis and Short indicate that it is quoniam instead of quonjam (despite being related to jam) but there is no indication of how the conclusion was reached.
The process of making a corpus search for metric evidence and parsing the output for a useful conclusion can take a while, and usually the end result can be condensed down to what would work in a dictionary: "quonjam would not scan right in Catullus 61.196."

Is there a dictionary of metric evidence for pronunciation?
Of course some things are hidden (like vowel quantity in closed syllables), but I would be happy enough with the metrically visible features.
(See this question for hidden quantities.)
They would also be easy to justify by quoting poets.

If there is no such resource, what comes closest?