Yes they are. We are replacing the left side cylinder heads on the 3.6 because of a misfire issue. There is a design flaw in the way the coolant flows through the head and it cooks the valve. (I work at a Jeep/Chrysler/Dodge dealership.) Have fun with that without the right tools!
No it wouldn't. Erase that thought from your mind. The 3.5 is an absolute gas-guzzling slug. Heavy and huge. Do you really want an engine and ultimately a transmission from an Intrepid? If your Slant is properly tuned it will provide decent mileage and acceleration.
That's because it's not really practical/viable/worthwhile. You'd be better off with one of the older 6 cylinders that were based off the Magnum engines, they should theoretically bolt up to one the older transmissions. (probably not a Slant 904 though) Still need to figure out how make it all work correctly, all that pre and early OBD stuff has been obsolete for years already.
Even if you paid someone to fab a turbo set up for your slant, you'll be way ahead. :cheers:
