As mentioned, Jeg's or Summit offer kits. However, you will go through them pretty quickly, so 20-30 roughing grit cartridge rolls wouldn't be unusual for you to use up on one head. The longer thin ones are good for getting between the valve guide bosses in the bowl area and the bigger short ones are better for the ports. I did write a very in-depth magazine article series on head porting just like the cam degreeing article I posted on another forum for you. I just don't have it saved where I could create a PDF for you unfortunately.

This is a very important step that is overlooked on most every porting job. Most aftermarket intake manifolds have a pretty wide port flange that you can drill a small 1/16" size drill bit through with no problem. With your head on a workbench and the ports facing upward, place the gasket on the studs first, then place the intake on like you are going to install it. You'll have to put a couple of washers and nuts on to hold the intake in place, but get it squared up as evenly as possible, then tighten lightly. Next, try to pick an inconspicuous spot on several intake flanges(one at each end of the head)to drill through the flange, gasket and into the head(only go into the head as shallow as possible). Next, just remove the nuts and washers and remove the intake and gasket. Get a couple of spare bits to insert in the holes for the flange you drilled while you coat the flange mating surface with machinist dye. Put the drill bits into the holes and stick the gasket on the matching holes you drilled so you can scribe the inside where the gasket needs to be matched to on both the intake manifold and cylinder head. Repeat this process for the exhaust next. When your ready to install these components on the engine before putting it in the vehicle, just insert the drill bits into the intake and into the head as you put it into position, tighten nuts and remove drill bits.

No they need to be attached separately since they are independent of each other in how they align to their perspective ports. If the intake and exhaust were cast as one piece, then yes. This is common to the Ford and Chevy inlines also, so don't think of this is a new concept.

Also, my copies of that particular article are long gone. It's been over 10 years since they were published. I guess i'll need to re-write one pertaining to the Slant at some point.