You should be able to easily ID between a Chevy SBC and a BBC by the width of the valve covers. The SBC cover is just under 5" wide (edge to edge). The BBC will be probably 2"-3" wider. (Sorry, I can't convert that to metric.)
If it's still an SBC, you can tell the difference between a 350 and a 400 by the harmonic balancer on the crank. The 350 balancer rim will be smooth all the way around. The 400 has a section about cut out.
A good site for Chevy block and head #s is Mortec.com.