From the datasheet, it looks like the P89v51 was never designed to source much current on the I/O pins. It just say the IO pins are pulled high when used as input.
On page 60 of the attached datasheet, Only P1.5, P1.6 and P1.7 has a max current sinking of 20mA, The rest of port 1 are 15mA current sinking. So in your case, if you use common anode 7 segment LED and with the same resistors, the current would not exceed 10mA on each segment then it should OK.
Allen