I'm going to channel Steven Snyder here...
What spring rates are you running or what spring rates 'will' you be running? What is your suspension frequency goal?
Do you want adjustable? Are you prepared rebuild/revalve yourself?
The bilsteins for the C3 corvette 24-009461 should fit with ~1/2" (10mm) spacers... Bilstein can put a snap ring groove into the shock for coil overs for 50-100$/shock. C3 corvette owners complain they are a little soft compared to the equivalent C3 Koni's.
Koni 8040-1019 or 1087 will fit with ~10mm spacers, have the same stroke as the 1988 front Konis and the 1019's have almost the exact same force velocity numbers. Koni sells coil over sleeves for the 8040s but the shock body has to have a retainer ring welded to the shock body.
If you want to go SN2 Bilsteins, available in nonadjustable, single, and double and are user rebuildable you'll have to drop the shock through LCA a few inches as the extended length is 15-16" and 11" compressed.
WCF sells Koni 30 Series shocks with mounts that drop them a few inches below the LCA ( I have a set of these and brackets I am selling if your interested currently listed here and on ebay.. )