New Engine, Bad Mileage

Put a rebuilt longblock in my '93 1,200 miles ago. Runs OK, but mileage is now 14.9 overall country and city driving. With the old engine, mileage was consistently 19-21 mpg for the same conditions, with 24-26 mpg on trips. I realize it will improve with more miles, but not by 5 mpg.

Any ideas on where to look first? I've already checked timing and set it a 0 degrees as recommended. This eliminated the "Service Engine Soon" light from knock sensor code 42, 43.

Info in addition to the above---On cold starts, engine runs lean for the first mile. Seems normal after that, except that low end torque (below 1500 rpm) is not as good as the old engine. Could the cam profile be different?