It comes down to how well Kalambay can handle himself on the inside. Fullmer excelled at spoiling polished boxers.
Fullmer probably roughs him him and outfights him enough to win a decision, much as I liked Kalambay.
I'd pick Kalambay. I think he's a better boxer than Giardello, and he's stronger than Robinson (and IMO, better than the old version who Fullmer 'beat'). He should be able to push Fullmer back better than Robinson did, while doing what Robinson did on the outside. I like Kalambay to jab Gene on the way in, and put some spiteful shots on the end of it to acquit himself nicely during exchanges. Fullmer's relentless style looks awful for boxers though and he he'd give Kalambay everything he's got. Sumbu SD15