70sSanO

You have a few options...

First off, there are no downtube, bar end shifters or dropbar mountain brifters.

You can get an M6000 GS, medium cage, and run your 39-30 chainrings in friction with an 11-42 in friction and and hit then numbers; Max Cog 42t, max capacity 41. Depending on your downtube shifters, you may or may not cover all 10 speeds within the 180 degree lever swing. But if it works, that is the cheapest way to go. If it doesn't work well enough for you for friction shifting, it does open up a can of worms.

You can get a 9 speed Deore 592 SGS and run a Wolf Roadlink with an 11-40 10 speed cassette, ('might" be able to go to 11-42) with your 39-30. The 592 SGS has a max cog of 36t without the Roadlink and a max capacity of 45. For that matter run it with 39-28 chainrings straight to an 11-36 cassette. You can then run in friction, or you can run in 10 speed "road" index with 7900 downtube or bar end shifters or go to a Microshift 10 speed downtube or bar end, or brifters, or Gevenalle shifters. Road 10 speed shifters will work with mountain 9 speed rear derailleurs and a 10 speed cassette. This option does open up the shifter selection.

Note: The can of worms would be a potential cable hack I saw done on an XT 10 speed Shadow Plus, to work with 9 speed mountain, which would make it work with 10 speed road. I would never recommend this to anyone else, but if I had a 10 speed road setup I would try just because I love any hack that works and goes against Shimano's blind eye to supporting older systems. The RD-M6000 attach is a little different, but it would be a fun test; but only if the rear derailleur is expendable if it doesn't work.

John