Its about time someone got back to the orginal topic and answered the questions of the topic starter rather than ramble on about which is better.
CA = expensive
L series = medium
A series = cheap

L series still a lot less expensive than a CA but unless u can modify basically everything yourself will still be quiet expensive. + to get the L series street legal will cost even more. Like dodgeman and nzdatman said, If your on a budget which most of us are(no money) than you cant beat the a series.

Oh yeah if u want a cheap engine upgrade by something like a torana or kingswood V8. you can fit any smalblock without modification. ie 307 to 400+