4.6 cobra 32v. Alloy block and alloy heads as standard. very easy and cheap to tune!!
I can measure the width as got 3 builds on the go at the mo and I'm sure Martin will measure his LS for you, I'd personally go with the easiest to get in the hole, Both can make great power and most people will only note that its a V8 rather than what brand it is
Martin's LS didn't appear to be much different in width to the ford modular.

The 302 small block is a nice size engine but the CAST steel block makes it pointless for an S1..