LS in an RX-7? Are you talking Chevy V-8 LS? I think the Wan kel (it won't let me say w a n k) Rotary in these is like 1.8 liters. I don't think anything bigger would fit. And I hear if you balance the motor and port and polish it, it can take something like 14,000 rpm! Though I have only heard this through the grapevine.
As far as the photo I'd say you did a good job of trying to create an accurate representation of the car. Which is nice. Some people like the overdone sky, and the HDR that looks cool yet totally fake. But yours is quality.
If you get the chance to reshoot this car, maybe try getting a wider shot. Also, see what it looks like with the overdone HDR. It may be something the owner of the car (or you) really like.