LOTS and LOTS!
I have researched this myself only to find that it is not something that I can afford right now

Well what you have to do is contact an RI... There is only one that I know of willing to convert Skylines. And that one place is Motorex and it will cost you any where form 15-20K for them to convert all nessesary things like the speedo, bumpers, smog system, make sure it is safe Ect....
I am not the most knowledgeable on this subject, but there is someone here who has Imported one himself for track useage...
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