My vote: I went with 1.5" drop Hotchkis rear springs that way I could add a spacer between the spring and the rear end mount to fine tune the stance. If you go 3" that's it no adjustment other than air shocks.
Don't get me wrong 3" looks good but you really need to make sure you have your wheel size and tire selection down pat for wheel well clearance.
The fronts I used 2" drop though I'm using a aluminum head BBC so basically same as SBC springs.
BB