Ford is working on a new Shelby GT500! Maybe. All around the car internet, we’ve seen spy photos and rumblings of a new, hotter Mustang and the name Shelby GT500 is being bandied about. Really, all we know for certain is that Ford is testing some Mustang prototypes based off the Shelby GT350.

We don’t know what these prototypes are, what’s powering them, or if they’re an indication that something cool is headed for production. But, there are too many rumors to ignore, so we’ve compiled them all here. And while we don’t know what this Mustang will be called (if it reaches production, that is), we’re going to refer to it as the GT500 from here on out.

The GT500 is seen as Ford’s answer to the 650-hp Chevrolet Camaro ZL1 and the 707-hp Dodge Challenger Hellcat, so everyone is predicting it’ll get a powerful V8. No one seems to agree on what sort of V8, however. As our colleagues at Car and Driver point out, both a new twin-turbo V8 and a supercharged V8 have been floated as possible GT500 engines.

Car and Driver thinks that the GT500 will go supercharged—specifically, with a 5.2-liter V8 similar to the unit used in the GT350, but with a traditional cross-plane crankshaft. The Instagram image you see above shows a supercharger housing with a Shelby logo and the number 5.2 stamped on it, which confirms at least some of Car and Driver’s speculation.

Motor Trend obtained a picture of a Shelby GT350 with a supercharged engine, claiming that what’s shown is a GT500 prototype, but that’s unconfirmed. This could easily be a prototype for a factory supercharger kit for the Shelby GT350, not necessarily a GT500.

Unfortunately, we have frustratingly few concrete facts about the GT500. All we have are rumors and spy photos to go by. But, we’re keeping a close eye on what Ford’s cooking up. It’s hard to imagine that it wouldn’t want to take a shot at the ZL1 and the Hellcat.