'Sugar, Sugar' Singer FLOORED by Davy's Death -- He Was in 'Perfect Health'

The lead singer of the 60s band The Archies -- famous for singles like "Sugar, Sugar" -- is completely shocked by Davy Jones' death ... telling TMZ, Davy was in "perfect health" just months before his death.

66-year-old Ron Dante -- whose group released several hits around the same time as The Monkees -- tells us, he was great friends with Davy ... and even spoke to him a few months ago, when Davy appeared to be doing just fine.

Dante tells us, he and Davy had been in discussions to do a show together not too long ago ... and possibly even cut a few records -- but those plans never materialized.

Dante adds, Davy "will be missed by millions."

Fun fact: The Monkees and the The Archies shared the same manager ... Don Kirshner.