John, you are correct, the Tony Kart Extreme and Esprit do not use a standard frame rail spacing, they are much wider than the European spacing that many sprint karts use. I would contact the mount manufacturer that Freddy suggested and make sure they have a mount that will be wide enough. I have several mounts here for my Tony Kart Extreme, but they are both kt100 bolt pattern mounts, not for 4 cycles. You may have to cut off the seat strut and modify the rear frame crossmember to get enough clearance to run a 4 cycle on that kart, depending on the motor mount you end up getting and exactly where the engine ends up sitting in relationship to those frame members. I personally wouldn’t cut up that kart, as it looks like its in great shape and would be a shame to hack it up. I would put it up for sale on here and buy a chassis designed for a 4 cycle engine first. The adjustable mounts can usually give enough clearance to miss the seat strut, but the rear frame crossmember is so close to the rear axle that you are limited to a very small rear sprocket.