Former Saltire McCallum (55) shared in a 130-run stand with man of the match Ryan Flannigan (84) as Zeeshan Bashir's six wickets for 49 runs proved in vain at New Williamfield in Stirling after the eventual victors established a platform through Scotland recruit George Munsey (29) and former under-19 batsman Nick Farrar (22).
McCallum said: "I thought the lads were outstanding. Clydesdale made it very difficult for us, especially their spin bowlers who kept things very tight. But we dug in and Ryan's innings proved decisive. It's a really proud moment for me and the club, and our success is tribute not just to the players but all the guys who put in so much effort behind the scenes."
Bashir appeared to have put Clydesdale in with a chance of winning the trophy for the first time since 1988, his spell restricting Grange to 222-8 after they had been cruising on 185-2.
However, the Titwood side's run chase appeared to be doomed from the moment Con de Lange, the former Northants all-rounder, fell to Raj Routray in the second over. Paddy Barbour and Sam Page then departed in quick succession to leave the Western Union side on 33-3, before Richie Berrington and captain Majid Haq set about repairing the damage with a stand that briefly hauled Clydesdale back into contention.
Berrington led the recovery with three consecutive boundaries off Nick Farrar before sending a straight six through the sightscreen at the Monument end off Andrew Brock.
Haq joined in by striking Arun Pillai to the long-on boundary for four and sent the next delivery over the rope. However, the Clydesdale captain's day came to an end when he was adjudged lbw to the same bowler. Convinced he had edged the ball, Haq briefly stood his ground before thumping his bat on the turf in frustration.
It proved a crucial breakthrough for Grange, who took another two wickets in quick succession to leave their rivals on 136-6. However, while Berrington remained unbeaten Clydesdale still had hope.
The former Greenock player, though, continued to run out of partners and was eventually second last out for 69, striking a Tom Sole delivery to Farrar at extra cover. Clydesdale were eventually all out for 184 when Sole claimed his fourth wicket.