Make sure you double check the interior dimensions, including how far the hump juts out. Would be a damn shame to get it home and realise it's only just too small.
Grab some sheets of paper and trace the keg bases on it,sticky tape them together to get the minimum floor area required and hit the white goods shop to find one that will suit,less chance of stuffing up a measurement.
Remember it also depends on the size of the kegs. The Coke kegs were shorter and wider and whilst originally pin locks, many have been converted to ball locks.
Spog's suggestion is a good one, but expect some odd looks