From GTP's very own GT3 car list
F090/S (F1, McLaren, Senna, 1990) '90 (US Only)
F094/H (F1, Williams, Hill, 1994) '94 (US Only)
F094/S (F1, Williams, Senna, 1994) '94
F686/M (F1, Williams, Mansell, 1986) '86 (US Only)
F687/S (F1, Lotus, Senna, 1987) '87 (US Only)
F688/S (F1, McLaren, Senna, 1988) '88
The 6 denotes a V6, the 0 is a V10. The next number is the year. The letter is the driver's surname (Senna, Mansell, Hill).
PAL drivers only got the F094/S and the F688/S, renamed as the Polyphony001 and polyphony002 respectively.