Streetracer, the LRP .28 version 3 engines are great. Good luck finding one. Another made by SH worth looking at is the Sh .28 P6 Prospec. The 528 XR will get anything moving fast-too fast for most guys frankly.
For a Revo steering servo the Ace Digital #DS1015 with 200oz. inches/.10 with 6 volts is all you'll ever need. Other servos that claim the same specs (Airtronics) are nowhere near as strong.