Well I figured out how to dump the D1771 chips. Just call me the ROM whisperer... turns out it's stupidly easy.
Fire up the chip, apply a clock, and pull pin 17 high. The ROM will now come out pins 5-1, then 28-19.
512 words come out followed by 3.5K words of 0's, which is exactly what you would expect because the PC is 12 bits. There was an unreleased? version of the chip with all 4K on it. This one only has 1/2K though.
1 word comes out for every 8 clock pulses. Reset will reset the PC back to 0.