I remember my family's two cats hid from the new dog for a good month at first. They never ended up liking each other (the two cats though brother and sister from the same litter didn't really like each other either), but they did learn to at least tolerate each other and respectfully keep some distance between them. The only time they ever grudgingly decided to get close together was in the winter when all three were hogging the space right in front of the kerosene heater though they very respectfully maintained a half inch of space between each other so they never had to actually touch.
Scavenger will eventually settle down though you might have to just wait for awhile on that. The cats will figure out if they want to be friends or just tolerate each other, and though it may take awhile eventually it will all work out.
It's so great that you decided to take this poor baby into your family. He'll live a lot longer and not have to face any of the hardships of outdoor ownerless life. You'll see. Not to long from now Scavenger will be a contented and well cared for and well loved kitty curled up in your lap demanding pets and purring away like a lawn mower.
I really love the name Scavenger that you chose for him. It's so perfect.