Chasing 309 for victory after the PM XI's sporting declaration at 4-221 late on day three, the tourists shut up shop at the fall of the eighth wicket with eight overs to go, finishing on 8-277.
Da Silva (52no) started aggressively before putting up the shutters in the last hour, while Reifer remained unbeaten off 26 scoreless balls.
Not expected to bat due to a groin injury, Reifer did not even look to score, declining even the easiest singles hit to the outfield.
The West Indies' most recent first-class win in Australia came in the fifth Test of the 1996-97 battle for the Frank Worrell Trophy.
Courtney Walsh's tourists - piloted by Brian Lara's century and Curtly Ambrose's seven wickets - thumped Mark Taylor's side inside three days at the WACA.
"It was just the right time," PM XI captain Josh Inglis said of his generous declaration late on Friday which paved the way for the nail-biting finish.
"We wanted to set up the game, which made today really exciting.
"It's a great occasion. Every time you're gearing up for international cricket, it's a great challenge.
"And to play against an international side is great.
"I think our boys had a really good week."
All results were possible when the West Indies entered the dinner break at 5-221, requiring a further 88 runs for victory off a minimum of 31 overs.
The last session started horribly for them when Roston Chase (13) succumbed after just three balls, beaten in flight by Ashton Agar (2-41), miscuing and lofting a catch to Joel Paris at mid-off.
The pendulum swung the tourists' way when Da Silva and Alzarri Joseph (31) combined for an enterprising 48-run seventh-wicket union.
Joseph, who swung lustily and impressively, was grassed on 24 by Aaron Hardie in the slips before guiding Mark Steketee (3-56) to Michael Neser at gully four overs later.
When Steketee had Kemar Roach (0) gloving a short ball to Peter Handscomb at slip, the West Indies fell to 8-273 and duly parked the bus.
Tagenarine Chanderpaul, the son of 164-Test legend Shivnarine Chanderpaul, was named player of the match for his fine double innings (119, 56), which should surely earn him a Test debut against Australia at Optus Stadium, starting on November 30.
"It was nice to get some runs," the softly spoken Chanderpaul said.
"I knew it was going to be tough ... just happy to get some runs."
Matthew Renshaw (81, 101no) and Handscomb (55, 75) hurtled themselves into contention for international recalls with their contributions for the home side.
