Vintage Synth Repair

Hi, I'm repairing a hopelessly faulty OB-X...I'm dealing with all the CPU and digital control side first....all the voice board faults secondly..

First question...it's packed with early cmos 74 series IE 74C174 etc...what are the best equivalents for these and other 74C types? 74HC? 40174 for example?

Second question: How long is the Autotune function supposed to run for? At the moment it stays on for about 2 seconds after button press...not that it seems to do much as it's hopelessly out of tune with various boards missing a VCO here and there...

Thanks, Philip.