techinspector... I like how you think
Those 2's are pretty light and small. You will be able to get away with a pretty wild small block and shave weight compared to a BBC. The Caddy is almost as light as the SBC and has a serious displacement advantage.
So, (even though I love BBCs) the SBC sticks out to me first. A 383 stroker can be built for about the same as a 350, but much less than a 454 and it has 84% of the displacement. But, getting a 383 to make the same power as a 454 is cheaper and since you have such a light car you can deal with the extra revs you'll need to get it.
The caddy is a wonderful engine since its huge and just a few pounds heavier than the SBC, but it costs about the same as a BBC to build and is a little less suited to revving. Of course you don't need to rev a caddy to make torque and power, but its a slight mismatch in my opinion. I'd rather see light cars matched with high-revving engines
So, when it comes down to it, I would personally do a 383. The Caddy is different and can still make the same power with 50% more torque, but at the cost of the little nitpicking things it requires to adapt it into the C2 chassis.
Either way... I vote against the BBC