Replacing tuners on Warwick Corvette

Hi, kind of a simple question but my bass is at the practice space an hour away so I can't measure for myself.
I'm looking to replace the tuners on my Warwick Corvette Standard 5. I've had trouble with them breaking in the past and the bass has some neck dive so I'm looking at swapping them out with Hipshot Ultralites. However, Hipshot offers 1/4" or 3/8" versions. Just wondering if someone had made this swap before and knew which one fit better on this model of bass.

Thanks to anyone who can offer some guidance.

 

Thanks guys!!!!