SAF_Zoom,
You are a long, LONG way away from needing to make engine choices. But since you asked, I think a 13B would physically fit either way in a LE. From what I saw of Perry's install, NOT plugs up would be better. Normal mounting would keep the exhaust to the side rather than on the bottom, and away from a bottom mounted radiator.
My personal opinion is, the 13B (and all it's associated components required to make it run and cool) is too heavy for a standard Long-EZ. One must keep in mind that the LE was designed for an O-235. (I installed an O-320 but do as I say, not as I do )
I made this offer to you once before... next time you're in Toronto, I'd be happy to spend some time discussing Lyc vs. 13B.