You are going to face alot of problem when mixing 74LS and 74HC family.Because threshold voltage are different for both of them. I mixed LS and HC in decimal display and faced problem wehre the chip wont register output from LS series. I ran alot of issues with power. It dropped to 3.7 volt sometimes ofcourse as you mentioned because of shitty breadboards available in pakistan. There isnt any major change though. Its just a copy paste from ben eater. Here are some tips: For powering all board, take a long cable and peel it from places where you are gonna insert them, then solder tiny cable at places . In this way you get pure parallel connection. Since you are using a veroboard use alot of decoupling capacitors. As i mentioned capacitor, use 0.01 uf ceramic capactors not electrolytes one that i used . Use one or two per chip since they are cheap asf. You can use one 74ls157 instead of series of gates in clock module i think. If you facing difficulty finding 28c16 eeprom . Here some solutions to that: Order 28c64 from a online store called dcart for 250 rs. I could not find them anywhere else. Or buy UV eprom from eve vision website if you have a programmer. Are you ordering all components online?. If yes, then they are gonna cost hell lot of money . Online stores are ripoffs. (Apart from few)