What part(s) have you let go, only to wish you had kept them not long after?

Hemi Crashbox with Liberty gears; 12" wide cop car wheels; spare 4-speed with Hurst Ram Rod shifter; '71 Duster with 440, 727 with manual valve body, 8 3/4 with 3.55 and powerlock, and 6 point cage.

Non-Mopar related: A huge box full of classic Harley parts (Panhead stuff mostly)