Ferrari spokesman Luca Colajanni spent a day at McLaren's Woking factory on Thursday, meeting team boss Ron Dennis and other staff.
"If you had told me a year ago that I would be doing this I would not have believed you," he said at a media dinner co-hosted by the two teams.
McLaren were fined a record $100 million (£70m) in 2007 and stripped of all their constructors' points for their involvement in a spying controversy over leaked Ferrari technical data in their possession.
Champions Ferrari also started legal action against their rivals, with Dennis and other executives questioned by Italian police. The action was later dropped after a McLaren apology.
Since then, the climate has changed with Jean Todt handing over as Ferrari boss to Stefano Domenicali while Dennis is due to step down as McLaren principal on March 1 to make way for Martin Whitmarsh.
The Formula One Teams Association was set up last July to represent the teams in talks with the governing FIA and commercial supremo Bernie Ecclestone.
FOTA is headed by Ferrari president Luca di Montezemolo, with Dennis and Whitmarsh visiting the Italian team's Maranello factor for a meeting last season as the urgent need for cost cutting became apparent.
Montezemolo, who has criticised Ecclestone's running of the sport, described Dennis earlier this month as "a first-class person from a first-class team" and said F1 needed great competition on the track and great unity off it.
While FOTA have agreed significant savings with the FIA for this season and beyond, they want Ecclestone to hand over far more of the sport's revenues to them than the 50 per cent they currently receive.
Dennis said that McLaren and Ferrari were "working extremely closely together" and he would devote more of his time to FOTA activities.
"The result of our cooperation, supported by all the other teams, has already been profound," he said.
"The cost-cutting measures that FOTA put forward were agreed by (FIA president) Max Mosley, when we met him in Monte Carlo on December 10, and were taken further when FOTA met again, this time without Max, in London on January 8.
"As such, FOTA has already achieved great things, and it will achieve even greater things in the weeks, months and years to come.
"We're not complacent; we're not reluctant to embrace radical change; we're not hidebound by on-track rivalries," added Dennis.
"No - working together for the good of the future of Formula One, we'll continue to devise powerful strategies and innovations intended to improve our sport so as to make it more affordable, more environmentally friendly and more appealing to spectators and TV viewers."