Month ago I bought two CMOS replacements for the CPU: MC68HC000. The advantage of this CMOS CPU is that it consumes less power. Unfortunately the replacement was not that simple as you think. The replacement came from China and were used chips. They were desoldered and some of the pins were bent. But after some gentle wiggling I managed to get all the 64 pins in the right holes...

The current in the system drops from 480 mA to 280 mA, so a reduction of 40%.

Besides the power consumption and therefor a lower temperature, there are no advantages for this chip. In the old days I had a PC with the CMOS replacement of the INTEL 8080, the NEC V20. This CPU was 25% faster on the same clock speed as the original. I remembered that all the chips on the board were warm, but the CPU keeps cool.