If you can lay your hands on a couple of TIL311 displays, that would do it. They had 4-bit inputs, latch, decoder, driver and display all together. The display was hexadecimal, so all you codes are covered.
Device is obsolete, but I saw a few sites on the net looked like they might have some left in stock.
DM74185A - check the attached datasheet - is a 6bit binary to bcd converter.
place it between output of your ALU and bcd 2 7seg drivers
hope that helps
EDIT: you can do it with only one bcd 2 7 seg as first digit is only 0 or 1 hence you can connect the pin Y4 (MSD-A) directly to segments that make "1" on first digit and Y1-Y3 to BCD input of bcd to 7seg (A input on bcd 2 7seg is lsb from your alu) so you will get "blank" first digit for 0-9 and 1 will light for 10-15 ... clear ?