Firstly, speaking for myself, I was joking about my remark. It was a direct quote from 'Starsky & Hutch'. If you were offended, I'm sorry, but you should see the film - damn funny.
Secondly, I think the attitude you have been given is probably founded by the fact that no one can understand how you could get a running RB26 for so little money. If you are able, and it is that cheap and legit, then that is awesome - we are all jealous. Can you put me down for 3.
Thirdly, why do you want to put an RB26 in the S15? You have to ask yourself some pretty serious questions about cost vs benefit. A well built SR will be reliable up to quite a number of kay-dubyas (i don't have experience, but may people build mega hp SRs). What sort of hp do you want? RB26s are expensive to make high hp (compared to SRs) - would it be more effiecient to spend all the custom fab cost of dropping in the RB on modifying the SR anyway? And would the chassis balance be ruined by dropping in another (guessing) 100kgs in the front end? eg. Meggala pulled out an RB20 from his Ceffy and dropped in a SR.
BUT - an RB S15 will be totally cool and unique. If you are out to build a unique or show car, then do it. It can be done (see zymotic's link), but unless you have mega resouces, may end up being high cashola if you want a 800hp motor
Oh and by the way, INASNT is probably the most negative person on the forums