* Futures down: Dow 43 pts, S&P 6.5 pts, Nasdaq 8.75 pts
By Yashaswini Swamynathan
March 31 (Reuters) - U.S. stock index futures were slightly lower on Friday as investors prepared to lock in gains, with Wall Street set for its best first quarter in four years.
* A raft of strong economic data and the possibility of fiscal stimulus under President Donald Trump has driven Wall Street to record highs since his election.
* The S&P is on track to gain 5.8 percent for the first quarter ending Friday, its best start to the year since 2013.
* Investors are also looking to the first-quarter earnings season to justify Wall Street's lofty valuations.
* The S&P is trading at about 18 times earnings estimates for the next 12 months against its long-term average of 15, according to Thomson Reuters data.
* However, the improvement also means more interest rate hikes by the Federal Reserve. New York Fed President William Dudley said on Thursday evening that it was appropriate to tighten monetary policy to reduce the risk of overheating the economy.
* On Friday, oil prices fell 0.8 percent after a three-day rally.
* A report on consumer spending and a measure of monthly inflation is due at 8:30 a.m. ET (1230 GMT).
* Shares of DuPont were up 0.6 percent at $82.11 in premarket trading after the company said it would sell its crop protection business to FMC Corp and buy FMC's health and nutrition unit in a deal that will give DuPont about $1.6 billion.
Futures snapshot at 7:01 a.m. ET:
* Dow e-minis were down 43 points, or 0.21 percent, with 15,093 contracts changing hands.
* S&P 500 e-minis were down 6.5 points, or 0.27 percent, with 106,278 contracts traded.
* Nasdaq 100 e-minis were down 8.75 points, or 0.16 percent, on volume of 18,096 contracts. (Reporting by Yashaswini Swamynathan in Bengaluru; Editing by Anil D'Silva)