LeSabre T type, Bonneville SSE (I know little about Bonneville), and Olds FE3 all had the performance suspension. Olds did not use the F41 "term" and Buick did not use the FE3 "term". The springs are all on the same charts., F41 & FE3 that is. Cars with self leveling rear air shocks(most FE3) will have lighter rear springs than LeSabre T-type F41. Cant speak of the Bonne'*.
The sway bars are heavier on F41 & FE3 cars as well. They also used a differently valved strut. Difference in steering rack too.
One LeSabre t-type owner said Sears believe it or not showed the heavier rate springs on their screen, this was a few years back but try them.
86 LeSabre coupe, 90 Regency, 90 Ciera Cruiser and the 97 LSS have a new stable mate............06 G6 GTP coupe, white with taupe & black interior