Here's a circuit from a kodak camera - this is the generic configuration of a ringing choke converter. You can't get too much simpler than this!

http://members.misty.com/don/kflashe.gif

The AVRs I used were a 2313 which was programmed in asm and a mega128 in C. No reason a 8051 can't be used, just that the timers in the AVRs are more suitable. If the 8051 has a PCA - excellent!

Your pickup circuit looks ok, but the devil will be in the details! The elctronic ignition systems in many of the newer cars tends to 'ring' a bit which gives you multiple triggers for each ignition event. This needs to be filtered out in hardware and software. If I'm feeling motivated, I'll see if I can sketch the circuit of my cheapy timing light.