Unfortunately, I don't know where to find the dimensions of the RB series engines. Being a motor that never officially saw US shores, may be tough to find. All I know are the displacements, which you prolly know by their names <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/tounge.gif" border="0" valign="absmiddle" alt='

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Hopeful:
THE RB series engines were basically made popular by the Nissan Skyline GTR, top end sportscar sold only overseas.
Breakdown of engine codes:
example VG30DETT
VG = engine's name essentially
30 = displacement, 3.0 liters
D = Dual overhead camshafts (per cylinder bank). Left blank for SOHC engines, and I've seen a V for variable valve tming engines (SR20VE)
E = Electronic fuel injection
T = Turbo
T = Another turbo