I did a search and cant seem to find a lot on this apart from someone making expensive carbon fibre ones.
However here is a cheap solution.
Buy 2 of these and epoxy glue them into your original stacks at the desired height.......... Simple.

VELOCITY STACKS HILBORN CROWER WEBER VINTAGE SPRINT CAR | eBay

 

Or you could just spend $130 USD for a set of trick AL ones.....

A&L Motorsports. Superhawk Parts

 

is that for a pair?

 

what is surface coefficient of friction between plastic and aluminum for wind?

 

Yes as far as i know it is the price for a pair....

 

That is not the big issue. What really matters is the smoother more controlled air flow from the precision machined units. The material is not all that important.

 

so shape and size. can you elaborate on stack height and why this curled lip aluminum upgrade makes a difference in how smooth air flows within a turbulent air capsule?

 

The height has an effect on what RPM range the stack flows the most air.

The curled lip give the air a larger radius to turn when entering the stack, thereby allowing the flow to smooth out. Also the smooth constant inner diameter of the Al stack helps here also.

Run your finger around the ID of a stock plastic stack and you will see what I mean. You can feel the molding ridges and lumps that they have....

 

Dont forget the rubber intake manifold too