Mattel Auto Race should have a Rockwell MCU, is the Sears one a newer release?

Yeah, TMS1025 is an I/O expander like the 1024. Did you trace it to understand how the chip works? If not, I'm sure we can find out with trial & error. A pinout would be awesome though: which pin goes to which LED, which TMS1040 pin goes to which TMS1025, etc.

TMS1040: can you see differences on the die when compared to the standard TMS1000?

kevtris: with more of those Konami (Mitsubishi, was it?) MCU dumps now, I'm confident enough to start a new mcu emu core =) - the more 'test cases' the better