Best macOS version for potential MacBook Pro Early 2008?

here are the specs:

512GB SATA SSD

6GB DDR2

Chip: 2.4GHz C2D T8300

Battery: Yes.

Thermal paste replacement: NO. My MacBook Pro A1278 died because of one.

Dust Removal: as much as i can without unplugging too much of the motherboard.

Fan Cleaning: yes