Mauro, welcome to forum. We’re glad to have you here!
Looking back, and hindsight being what it always is, you probably would have been better off to keep the 66 GTO. That car became an icon for the mid 60s muscle cars, whereas the Pontiac LeMans GT-37 was forgotten, even with the small production numbers.
I owned a used ’71 Pontiac LeMans Sport, 350 V8, Auto trans back in the day (1975 to 1978) that I drove for several years. It was a nice sporty car with no mechanical issues whatsoever.