dont know the exact bits needed, maybe there are revealed in ken oconnor's "diy porting videos" ?????
but do know my local ace hardware and lowes carries all types of bits for dremel's as singles and kits
yep the tungsten carbide cutters are the best. usually you can find some sweet deals on ebay. make sure they are carbide or the the sleeve will destroy them in a hurry.
You could but like two bits separately and do the porting job but the set is nice because it gives you a bunch of choices to get into tigh areas and stuff.
Also, you can purchase the sand paper drum rolls from hardbor freight or northern tools with the mandrel included for about $7. It comes with an assortment of 10 different tubes and a mandrel.
Ken tells you all about the tips and cutters he uses in his self porting videos. There is about 5 of them on youtube but he posted them here first in a thread and that thread is stickied at the top of the engines section.