Which B18... B1, C1, C5?

Also, what model year is the car?
From 90-93, the RS/LS/GS models came with the B18A.
From 94-01, the RS/LS/GS models came with the B18B1.

303 whp you say? On a stock motor, the B18B1 Greddy kit only gets you to about 180 whp on 91 octane. I get the feeling that the seller isn't being straight with you.

If he's built the motor to handle 300+ hp on a daily basis, don't you think he'd have pictures to document the build-up?

Call me a skeptical bastard, but my spidey-sense is going off. Something ain't right.