Voltage regulator with Vin up to 40 V DC

Hi all:

I have a circuit that needs ~ 35 volts DC (unregulated) @ 8 AMPS to drive a flyback primary coil and a oscillator controller circuit using a UC3844 that requires 18 volts regulated + DC @ 500ma. My stepdown 8 amp transformer gives ~27 volts from the 120 v mains and after full bridge rectification and filtering I get 37-38V (no load). I want to use the same transformer for both parts of the circuit. It is center tapped. I can use an LM7818 and a few series diodes to drop the input DC voltage from the transformer to below 35Vin (max for the LM 7818) or an adjustable voltage regulator like the L200.

I thought the the L200 would be a more versatile solution since I could eliminate the voltage dropping diodes. Any thoughts?

What are the differences between the L200, L200C, L200CV, L200CH?

Where can I purchase just 10 pieces without the shipping costing more than the parts?

Is there another more available adjustable voltage regulator that can tolerate 38-40 volts DC in (rectified AC, filtered DC) and output 15-18 volts at ~ 500 ma??

Here is the circuit: volny.cz/jmartis/qrv4_en_final.png

Thanks for the help