What are your plans for this car? Road race/course, autox, drag, show, or touge? The only two uses I see an RB25 for are show and drag. Otherwise, all things point in the SR20 direction.
OTOH, if you put the RB25DET in, you can always say that you have a Skyline engine in your car. <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt='
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If you slapped 8k in my hand and told me to spend it on my car, I would have an SR20DET w/ GTi-R turbo running light boost (10psi or so?), 444cc injectors, full coilover suspension and Do-Luck products throughout the car.