whats a slant 6 worth ?
The exhaust manifold is the most valuable part since they crack, up to $100 even used on ebay. If installing the exhaust, search for the info on how to orient the washers so it doesn't later crack. Too heavy to ship affordably, so a local buyer via craigslist. Blocks with 5 core plugs, thicker front web, and forged crank are said to be preferable (~1974), at least for racing, though I'm not expert.
Most people give away a slant and its transmission since so many rip them out to install a V-8. I have a spare slant from a member here who just needed it gone. I should also give it away since just taking up space and may never get around to using it. If I move, I'll surely give it away.