Realising that the bolt is used in three places and from your conversation, I'd agree that the bolt is nothing special and original. That your spacer is shorter than the combined length of the bushings would indicate that the suspension travel shouldn't bind unless the spacer is still too long once it's compressed and carrying a load. I drew a scaled cross section with a 2.5" long spacer as found in the photos and the 1" and 2" bushing without being compressed. Probably of no help, it's attached just in case. Was hoping to help you solve this without having an original piece to measure. Good Luck!
1959 J Convertible
1960 J Hardtop