At route 37 you can catch:Stantler,growlithe,pidgey and rattata.
you can catch a growlithe at route 37.
You can only catch Vulpix in SoulSilver, not in HeartGold. You can catch it on route 36 and route 37.
Route 36 and 37
in Pokemon soul silver catch it in route 36, route 37, and route 48. (Note that i don't know if it is the same for silver)
You catch Snubbull in Route 37 and 38
Route 36-37
You could either trade from red/yellow version or I have heard rumors of videos that tell you about a glitch to catch him.
Catch a Vulpix on Route 7, 8, 36, 37 or 48, then evolve it using a Fire Stone.
Well, the easiest way is to just choose Cyndaquil as your starter, but if you didn't you can catch a Growlithe on route 37 south of Ecruteak City.
Route 1, 2, 29, 30, 31, National Park, Route 36, 37 and all at Night time.
You can catch Snubbull on Route 38 & Route 39
You can catch it in Route 2.