I think the Vibro King is the best amp Fender has ever made. It has the Fender reverb, the separate Fedner unit, built-in. The tone is amazing.
I don't get why someone would want to mod it to sound like a Super. Get a Super!
The VK has more of the tweed thing going, especially cranked. A Bassman definitely is a lot closer to the tone than a Super.
Drawbacks is the VK is freakin' heavy!!!
The best Fender tones I ever had was my '57 AVRI Strat and the VK, from beautiful clean tones, to outstanding overdrive, great for blues, or anything else really.