it sounds like an exaust problem, or maybe leaf springs. More then likley it is the exaust... your rubber bumpers should be around the tail pipes.... get under the car and rattle the exaust and see if it makes the same noise as when you go over a bump....
It could be a lot of things, but your use of the word "jingle" reminded me of a problem I ran into with my 67- it sometimes made a "jingle" sound when hitting a bump. As I remember, when I replaced the rear shocks, I discovered a problem with the rear mount where either a washer was missing, or something broke, so that one washer was not pressed against the rubber bushing like it should - it was suspended a little and that allowed it to jingle against other metal when I hit a bump. THe sound drove me nuts for months until I figured it out.
Check this and the suggestions in the other posts. Good luck
1967 Fastback, 289, C-code, AT, PS,
motorsport intake and valve covers, Edelbrock 4V, cam - otherwise stock
dark moss green, parchment interior,
GT rear valance and tips