hi hussein
Can you get a EPROM or EEPROM programmed by anyone.?
Consider a 8 * 256 EEPROM.The type of EPROM that is addressed with 8 lines and has 8 data lines. They are not very expensive and it would a simple solution for the Bin to BCD decode. You will require 2 EEPROMs
Program them with a Binary to BCD decode pattern.
As you are only adding two max values of b1111,1111 the max sum will be b1,0000,0000
[0xFF, #255 requiring, 8 bit address] .
ie; The ROM addresses would be the Binary 8 bit byte output of the 2[4+4] bit adder and the Carry bit. The data output from the ROM would be arranged as two BCD bytes, which would drive the two , 7447's