The eight-year-old has won and been second on his previous two trips to the borders track and returned after a year off at Newbury in December.
"He's been running over further so he should be better back over a course and trip he has gone well at in the past," said McCain. "He's run in some tough races and is very high in the handicap so the conditions of this suit, too."
The field is completed by Duke of Navan, Morning Royalty, Pas Trop Tard and Orsippus, who ran at Musselburgh yesterday.
Dual Scottish Grand National hero Merigo is ridden by Jamie Hamilton in the Amateur Jockeys Association Amateur Riders Handicap Chase. Timmy Murphy, the man on board for his two wins at Ayr in 2010 and 2012, said: "He is a spring horse and hopefully he'll be back for another go at the Scottish National in April. I once rode him on top of the ground and said to Andrew Parker and his owner Ray Green never to run him on that again but it turned out that is his ground."
Peddlers Cross heads for the Ladbrokes World Hurdle after beating Cue To Cue by a length and threequarters on Musselburgh's final jumps card of the season yesterday.
"He had been a little bit noisy that's why we had the tongue-tie on," said McCain, the winning trainer. "Jason [Maguire] said the longer trip of the Cheltenham race will suit."
Lucinda Russell kept her good run going with Wild Geese in the 2m 4f handicap chase under stable jockey Peter Buchanan and Jedburgh18-year-old Callum Bewley enjoyed his first winner under Rules on Knight Woodsman for Ayrshire handler Mike Smith.