The lightest (looking) set up that i have seen is several members here have laced up motocross style excel wheels and spokes. if you are looking for light and strong wheels, the motocrossers have that covered. as far as your trail, we all know these aren't modern super bikes. to change your trail you might want to call around in the flattracking world and get a set of adjustable trees. i have a set on my dirt tracker (with R6 forks) but they make them for vintage bikes with 34 and 35mm forks. A&A racing, WEISS (sp?), there are several people who make them. If you aren't familiar with them, they use different cups in them and you can changed them very quickly to match track conditions. PLUS...they are billet aluminum, reducing weight...but it is sprung weight. if you'd like a picture of my adjustables, i could provide such over the weekend. another thing in handling is rider and motor position. even a full tank of fuel changes handling. good luck in your quest!!
My vote is for weight first also. Go with the lightest tire and rim you can use, decent but reasonable weight brake. Remember, reducing tire/rim weight reduces rotating AND unsprung weight. (I use the aforementioned Excel rims, Dunlop tires and a T500 brake...tire/rim is probably 5 lbs less than an OEM setup...and that's all unsprung, rotating mass).
With the rake on most vintage bikes in the area of 30 degrees I don't worry about trail unless there is some stability problems, too much head shake etc.
tapered steering bearings (so you can tighten them down and still get smooth steering) and one of those NHK steering stabilizers will solve your head shaking problems, well, as long as your frame is straight.
at the risk of sounding like i don't care about weight (which i do...i road race bicycles as well as vintage bikes), i think the behavior of a front end and therefore a large portion of a bikes handling character, is most effected by trail. a bike can go from handling like a pig, to stable, to nimble/"light", and finally to twitchey/unstable all with changes to trail.