It will definitely cost you more to convert to carb after you buy ignition stuff, carb, intake etc. I would make sure if you are going to use the ls6 intake buy a good quality plate kit. I like Nitrous Outlet personally , but there are other vendors also. I think it is possible for sure. You don't give up a lot of HP on motor over a carb setup with the EFI. I think it would be very possible to get in the mid 11's on motor, but I would probably at least have a valve job and maybe a little bowl blend on your heads. If you can get into the 11.50 range on motor then I think you could get into the 9.70 -9.80 range on 225 hit. Of course like we said already , it's all about the whole combo. Nitrous tuneup ,converter and getting the 60ft times is going to be the difference