Andrew Allen was gunned down in the front downstairs bedroom of his home in Buncrana on February 9th last.
Now Gardai are looking for information from anybody who may have seen the grey Vauxhall Cavalier car in the month before the assignation.
One man in his 50s was recently quizzed about the murder but was released without charge.
Garda Inspector Pat O’Donnell said the investigation was going well but they were very interested in finding out the movement of the car which was later found burned out after the murder.
Insp O’Donnell said: “It is now over two months since the callous murder of Andrew Allen at his home at Links View Park, Buncrana in front of his partner, Arlene on 9th of February 2012.
“The investigation into his murder is progressing satisfactorily with the valued assistance of members of the public who have come forward to date.
“I now wish to make an appeal to any member of the public who observed the grey Vauxhall Cavalier registration number SJI 2117 either parked or being driven during the month before it was used in the murder of Andrew Allen on 9th February 2012.
“This car is distinctive in the it was clean for its age and was equipped with a tow hitch, a sunroof and was missing a front wheel trim.
Anyone with any information is urged to contact the incident room at Buncrana Garda Station on 074 93 20540 or to call the Garda Confidentional Line on 1800 666 111.