your mechanic is full of shit, on some engines this is the case (torque to yeild bolts) but not on Toyota's. They determine the reusability of a bolt by checking the stretch. When they have too much stretch they get too thin and have to be replaced. This is right in the service manual if he doesn't want to listen to some random on the internet. I would trust Toyota bolts that have been used a few times over those non new non-genuine bolts that are probably chinese.
Also if you buy a gasket set they should come with valve stems.
That's pretty much what I said, everyone says yes awesome. Once they hear the price they will be really quiet. Anything like this is worth serious cash, people think they can buy a custom head for the price of an old second hand K motor
That's a first gen bigport head. If your really motivated change the valve stem seals and port the head while your at it. Otherwise they arn't known to have any issues.
The only 4age with the Distributor on the rear of the engine is a 20V?
Anyway a lot of your answers are in the FAQ section on this website:
http://www.rollaclub.com/faq/index.php?title=Tech:Engine/A_Series/Converting_to_RWD
look at the link at the top of this page
K20 engines do indeed spin the "correct" way like the F20C's. I don't like the way the JSP install of the Honda engines is done because he uses massive crossmember spacers.
apparently the front wheel drive 4ac engines didn't have the holes tapped for the engine mounts. Which isn't a hard job really assuming the holes are already the right size