I'm sure Dubb still makes the RO Jett 61 RE and it's a great running engine either on a pipe like Brett's or on a header muffler! Not cheap! But likely the best available today, unless you can find a good PA65.
If you're looking on the cheap, (uhhh well cheaper) the OS 55AX with a .170 diameter venturi and a tongue muffler makes a very acceptable large engine. Much more controllable power than any ST60 etc., and not difficult to handle! 13-4 APC Prop and around 9600 RPM on the ground gives a really good fast 4 stunt run. It will fly any of the current "Big" airplanes with aplomb! Also OS reliability and parts supply is a plus!
Also, Randy Smith does a Magnum.52 that will also fly any of the big airplanes and runs very, very well. As a plus it's a beautiful engine and Randy's B&B Mods make it a Peach. I don't remember how much mine cost but I think it is was reasonable!
Randy Cuberly