Who's running low 10s with leaf springs?
You don't have to install a full cage if you back half a car. As long as you leave the stock floor in place from the firewall to behind the front seat you can use a 8 point bar.
Let me also add that while it may seem more expensive right now to back half the car it really isn't in the long run. I've run SS springs, the CalTracs with their split mono leafs and now I'm building a four link. Since you are already talking about a low 10 second car do yourself a favor and four link it now. You'll be bucks ahead in the long run.
Yeah I know there are guys out there running 9's with CalTracs and/or SS springs but I'll bet $100 they aren't consistent at every track. At least the CalTracs are adjustable, but the four link is the setup to have. You won't need another ever.
I'm a bracket racer and consistency is the name of the game, leaf springs are not going to provide that for you.