Richard,
This is out of the realm of my knowledge on the ZL-1 blocks.
If it is a Can-Am block, perhaps someone here can help you
figure out the approx. value. I however think your assumed
value is very high. The ZL-1 blocks are bringing crazy $$,
but I don't think this one fits that category.
Take a look at this recent eBay auction for a Zl-1 block
for reference. Good luck!
ZL-1 auction
Steve