The HR series is very light and compact, more compact than the sand cast CR series
the bellhousing lends itself to modifying for a larger RWD box
http://soulsteer.com/wp-content/uploa ... ndia-Hall-number-12-4.jpg

remove the ancillaries eg. air con, power steering, front timing cover top mounts
and you have a very short engine with big bore short stroke capable of good rpm
and plenty of valve area as Simon suggests, 76mm 1mm all round is very possible.
L3 would almost make it a midmount setup with plenty of intercooler or space
in general for a good turbo setup even a well setup compound setup?

HR10DE K12 March / Micra 2002–2004
1.0 L3 (999 cc) 78.0mm 69.7mm 11.2:1
56.6 kW (77 PS) 98 N·m (72 ft·lbf).

http://www.nissan-global.com/EN/TECHNOLOGY/OVERVIEW/hr12de.html