Changes

The 74LS74 and 74LS153 are both widely available and very cheap because they are still in production. Although the 41256 isn't produced any more, they were used in many computers and other devices in the 80's and 90's and can be easily and cheaply found in many online auction sites.

The first thing you need to do is carefully remove the 8 64K RAM ICs (Usually Part No. NMC3764N-15) and store them somewhere safe (you never know when you might need them).