Feasibility?
Ryan is correct. But more, lets crunch a couple numbers. If you go from the DI to carb or carb to DI, it's going to cost more than it's worth. You'd be better off just buying the carb model GTX.
Just the mpem and carbs alone would set you over $2200 to $2500, pending on where you got the parts from. Then, you'd have to look at changes in the fuel system, throttle body and a few other small items. I'd say, you'd probably be looking at close to 3K before it was all said and done.
For as much as I personally dislike the DI (just my opinion), I'd recommend you stay with it. Also, from experience I have from listening to all the forum members that own the DI, this is one of the best fuel systems, performance wise, that you can get on the PWC........that is, if it's working correctly.
You blew a piston. The first thing to do is determine the root cause why it went out. If it's the oiling system or a lean condition from the injector or air compressor system.......