Based on my research this Used Spare Tire J-Bolt (GM # 1386521) and Wing Nut are for various 1965-1972 Oldsmobile models as shown in the 1972 Oldsmobile Parts Catalog (Jan. 1972) in Gr. 7.632 (see photos #8 & #9). GM # 1386521 is also listed in the 1972 Buick Parts Catalog for various Buick models. It may be an original factory assembly line J-bolt or it may be a service part. Currently on Ebay (not mine) there is a N.O.S 1386521 J-bolt & wing nut for Big $.
The J-bolt measures about 8" in total length (7 3/4" effective length) with a bend about 1 3/4" from the bottom end and a bend about 4" from the bottom end. The threads are 3/8"-16 and 2" in length.
The J-bolt and wing nut are in very good condition.
$25 plus shipping from 03054 (N.H.) and PayPal fee (if applicable).
If interested, send me a PM.
Dave