Jared, it comes up in fast as a genuine Spec R, 6MT (when it left the factory in japan it had the SR engine that you want). however as me mate Aus noticed, the intercooler cold pipe has got a S14 resonator on it?? the owner may of just put a S14 side mount in, may have removed a front mount who knows, as its missing the shroud for the fan too so it has been tinkered with but then again 90% of Silvias have, its no cause for alarm, or it may have had a engine swap. Ask him to email you a photo of the injectors DONT ask him what colour they are, purple are S14 turbo or S15 turbo automatic 380cc, orange/terracotta are S15 manual turbo 480cc, and a couple of good photos of the engine bay, if you go up and have a look at it, take a pen mirror up with you and look for the plate on the turbo center housing for this number 14411-91F00, that way you will know its got a Spec R T28BB.
If the rocker cover has got nuts holding it down then you have defiantly got a early S14 engine, but i cant speak for the later 97, 98 S14 SR20DET's they may have bolts holding the cover down like the S15 SR20DET's did.
If looking at it, listen to the engine idle very carefully, learn to define between injector noise (sharp very short clicking) and noises like lifter tick, VVL rattle and rod knock, also go to the back of the car and get someone to give it a little rev and look at the exhaust for blue ish smoke.
Listen to the gear box, noise clutch in and clutch out, go through all the gears ( all 6 forward ones ) feel for worn syncros,
Hell its worth booking the car in with ST Hitec for a 15min look over as in getting the guy to meet you there, wont cost too much and Soichi will tell you straight away if there is anything not right, i recommend him as he was in nissans engine design team when he was in japan.
Look for these bits on the car too,
http://forum.s15oc.com/showthread.php?9933-JDM-Spec-R-Body-Bracing-info-compared-to-JDM-Spec-S
is the cluster black like yours or is it silver?
if you havent figured it out all ready, dont take the sellers word for anything, everybody lies when selling cars