Assuming you need a frame for the '71 Buick & It's a 2 door Hardtop/Convertible, These are the Frames that fit....
Buick Special '68 2dr.,conv
Buick Special '69 2dr., exc GS400 H.T.
Buick Special '70 2dr., conv
Buick Special '71-72 2dr.,exc 8-455
Chevelle '68-'72 2dr.,exc pickup
Chevelle '71-'72 2dr.,H.T.& conv
Olds F85 '68 2dr.,conv
Olds F85 '69 2dr
Olds F85 '70 2dr.,conv
Olds F85 '71-'72 2dr
Tempest '68 2dr.,conv
Tempest '69 2dr
Tempest '70 2dr.,sdn., H.T & conv exc 8-455
Tempest '71-'72 2dr., exc 8-455
(Tempest also includes G.T.O. and LeMans. Olds F85 includes Cutlass and 442. Buick Special
includes Skylark and Gran Sport/GSX.)