Derailer-derailleur, the first is the English way and the second is French, the bike world uses the French spelling. We should also use the tyre spelling instead of tire since that would show the difference between being tired and riding on a tire. I also prefer the Shamano spelling over Shimano due to the Sham part more accurately defines the company...eek must be a Saturday.
My Shamano Deore, XT and XTR works with 38 Shamano gears but according to a bike mechanic about 5 years ago was that Shamano works with Suntour. My road bike has all Suntour Superbe components and when the Suntour Winner Freewheel wore out I replaced it with a Shamano with no problems.
Also supposely Sram and SR Suntour makes a derailleur that works with the 38 tooth gears. It may be easier to just change out the freewheel to Shamano since they are cheap at around $25 and then use whatever derailleur you have.
BUT I am not an expert on the 38 tooth situation, I'm just going by memory on a conversation I had with a mechanic that wasn't a conversation I took much interest in since I wasn't doing that. Hopefully a wrench will respond and correct what I said.