The striker scored more than 80 goals in five seasons in the Northern Irish Premier League and is eager to test himself in Scottish football for the first time.
The Scots-born 25-year-old told the Telegraph: "I scored around 80 to 85 goals in five seasons for Ballymena, which is pretty consistent.
"There was a £48,000 offer from Linfield a year-and-a-half ago but the club refused it so I missed out on the chance to go to one of the bigger clubs in Northern Ireland. But there was no way I was going to miss out this time.
"It's a big step up and I know I need to get a good pre-season behind me in order to make the grade. But I wouldn't have taken the chance if I didn't feel confident in my own abilities.
"I have a good touch and am good in the air. My goalscoring record is pretty good and I'm a decent passer.
"Allan Moore said Morton are a good football side and that Peter Weatherson is a good target-man who needs the right man to play around him."
Kelbie, who is based in Dunipace near Cumbernauld, trained with Stirling Albion, Moore's former club, through the week and would fly over for Ballymena games at the weekend.
With his contract up at the end of last season, he had the option to stay in Northern Ireland but jumped at the chance to join Moore's Ton revolution.
He added: "I was probably going to sign for Portadown when Allan phoned me. I know he is a really good manager through training at Stirling.
"He knows exactly how to get the best out of the players and is never off the training ground."
Kelbie came through the ranks at Rangers and moved to Alloa youths for a year before taking up a soccer scholarship at Northern Oklahoma College in the United States.
He returned home after six months and went on to sign for Ballymena, where he has become a fans favourite. He said: "I am 25 and feel I am at the right age to take the next step. The Northern Irish league is a good standard.
"Four or five of the national team squad play in the league and you only need to look at guys like Ivan Sproule who moved from Hibs and is now at Bristol City."
l Stevie Masterton, who was released by Ton at the end of the season, is a transfer target for Ross County and Crawley Town.