Why do you think older FD lenses are better than FDn?
This website's tests seem to show that the FDn 50mm 1.4 and 85mm 1.8 lenses are better than their older FD versions:
http://web.archive.org/web/20080101211626/http://www.members.aol.com/canonfdlenstests/default.htm
Canon FD 50mm f/1.4 breech mount (pre-S.S.C.)
Canon F-1 with mirror and diaphragm prefire
Vignetting = C+ @ f/1.4, B @ f/2, A- @ f/2.8, A thereafter
Distortion = slight barrel to none
Aperture Center Corner
f/1.4 B- C
f/2 B+ C
f/2.8 A- B
f/4 A- A-
f/5.6 A- A
f/8 A- A
f/11 A- A
f/16 B+ A-
Notes: moderately low contrast at f/1.4; moderate high center contrast and moderately low corner contrast at f/2; moderately high contrast at f/2.8 through f/16.
Canon FD 50mm f/1.4 breech mount (S.S.C.)
Canon EF with mirror and diaphragm prefire
Vignetting = C+ @ f/1.4, B+ @ f/2, A- @ f/2.8, A thereafter
Distortion = barrel
Aperture Center Corner
f/1.4 B- C
f/2 B+ B-
f/2.8 A- A-
f/4 A- A-
f/5.6 B+ B+
f/8 B+ B+
f/11 B+ B
f/16 B B
Notes: moderately low contrast at f/1.4; moderate contrast at f/2; moderately high contrast at f/2.8; high contrast at f/4 and f/5.6; very high contrast at f/8 through f/16.
Canon FD 50mm f/1.4 bayonet mount
Canon AE-1 with self-timer only
Vignetting = B @ f/1.4, A- @ f/2 and beyond
Distortion = slight barrel
Aperture Center Corner
f/1.4 B C+
f/2 A- B-
f/2.8 A- B+
f/4 A A-
f/5.6 A A
f/8 B+ A
f/11 B+ B+
f/16 B+ B
Note: moderately high contrast, except f/1.4 to f/2.8, where corners are moderately low in contrast.
Canon EF with mirror and diaphragm prefire
Vignetting = C+ @ f/1.4, B+ @ f/2, A thereafter
Distortion = barrel
Aperture Center Corner
f/1.4 B B-
f/2 A- B
f/2.8 A- A
f/4 A A-
f/5.6 A- A-
f/8 A- A-
f/11 B+ A-
f/16 B+ B
f/22 B B
Notes: different sample than above. Very high contrast, except moderately high at f/1.4.
Canon FD 85mm f/1.8 S.S.C. breech mount
Canon EF with mirror and diaphragm prefire
Vignetting = B @ f/1.8, A- @ f/2.8, A thereafter
Distortion = moderate pincushion
Aperture Center Corner
f/1.8 D+ C
f/2.8 C+ C+
f/4 B- B-
f/5.6 B- B
f/8 B B
f/11 A- B
f/16 B C+
Note: moderately low contrast at f/1.8, f/2.8 and f/16; moderate contrast at f/4, f/5.6 and f/11; moderately high at f/8.
Canon FD 85mm f/1.8 bayonet mount
Canon EF with mirror and diaphragm prefire
Vignetting = B- @ f/1.8, A- @ f/2.8, A thereafter
Distortion = pronounced pincushion
Aperture Center Corner
f/1.8 B- B
f/2.8 B+ B
f/4 A- B+
f/5.6 A A-
f/8 A- B+
f/11 B+ B
f/16 B- B-
Note: moderate contrast images at f/1.8 and f/22; moderately high contrast images at f/2.8 through f/5.6 (the optimum aperture) and f/11 to f/16; high contrast images at f/8.