RE: T-38 'Talon' propjet from Bob Cambell RC kits..
You do not need the perry carb, just the pump. Use the stock rossi carb.
The current perry pump adjustment is pretty good. Set up the engine first without the pump (on the test stand). Get the needles right. Then install the pump in line. Adjust the PUMP until the top end mixture matches what it was without the pump. Then you may need some minor tweeks to the low end needle.