whats a slant 6 worth ?

Yup. When I built my most recent one over the last couple of years I spent more on this engine than any car/truck engine overhaul I've ever done.
No more rebuild for $800. I remember doing about any small block v8 for around that, around 1/2 machine shop and 1/2 for the rebuild kit. Did more of them back then. Can't hardly do a set of heads for that anymore let alone the short block. I have about that much in this one head on my /6. And that's with me spending many hours making grinding dust on it before it went through the machine shop and buying the assortment of carbide burrs that I had to buy to do what I did to it. Exhaust valve seats, oversized valves, too.
I have that $400 just in machine shop fees in that head besides parts and burrs mentioned.