The pair will begin at their new clubs on Monday, the Tigers picking up the last three years of centre Olam's contract from the Storm.
Blore, also on a three-year contract, was reportedly set for a move to the Storm from 2025 but will now arrive a year early.
Olam's signing with the Tigers follows that of Penrith superstar five-eighth Jarome Luai last week and the departure of recruitment boss Scott Fulton.
The popular Papua New Guinean won a title with the Storm and was crowned the Dally M centre of the year in 2021.
But the hard-running 30-year-old fell out of favour with coach Craig Bellamy in his sixth and final season last year.
"Justin is a world-class player who will bring plenty of experience to our team," Marshall said of his recruit.
"His leadership and communication will be very valuable to our club."
Olam said Marshall's "vision" for him at the Tigers had excited him.
"I'm keen to put in the work and win the trust of the boys and the coaches at training, and hopefully contribute to what the club is building," he said.
Penrith junior Blore, 23, played 33 games in his four years at the Tigers and missing the entire 2022 season through injury.
"It is always difficult to say goodbye to players who have made such a great contribution to our club like Juzzi (Olam)," Storm boss Justin Rodski said.Â
"But it also presents both he and Shawn a new opportunity to continue their careers in a new setting."
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