All the work was done on the actual engine for which I was building the runners.

The intake manifold runners are made from mandrel bent 6061 aluminum
tubing, which I cut and had TIG welded for me by a local sprint car
builder. The tubing is available from Burns Stainless in Costa Mesa, CA

Notice in these images,  that the length of the horizontal runner (after the bend) is not equal.
That's to compensate for the offset in the stock manifold log's carburetor placement.
Due to these unequal length of these horizontal tubes, the completed intake runner system
is equal length,  from the off centered updraft Stromberg to each stock log.

By popular demand,  I'm adding some info about milling off the flange
and adding the new 1/4" plate flange I had TIG welded in place.

It all started with making a plywood jig in which I could place the head,
and "mill" the cast flange (carb base) off the top of the log.

Another view of the plywood jig.

Then with my angle grinder,  belt sander Dremel with sanding drum,
orbital sander,  and hand sanding,  I got it to this point.  From here it was
polished on a buffer wheel,  using 3 different grits of rouge.

Although I don't have photos of the next step,  I fashioned 2 matched pairs 
of flanges,  one pair for each head.  My son is a VW enthusiast,  so there
just happened to be a stock VW carb base gasket kicking around on my work bench,
so I used it for a template to cut the flanges to it's exact shape.

The round hole you see in the photo above is the stock hole that goes
through the carb base I routered off.  I don't recall the ID of the gasket I
used for a template,  but my welder asked that I make the ID of the flange
just slightly larger than the opening,  to produce s "step" for him
to weld the 2 pieces together.  So the ID of the flange is about 3/16" to
1/4" larger than the stock opening.

This shows the flange welded in place,  with no interior grinding.  The weld
was belt sanded flush with the gasket mating surface,  but some of the weld
reduced the opening size.

Additionally,  you can see that I've tapped this 1/4" piece of plate aluminum,
to receive the allen screws.  These screws (with 1/4-20 threads) were tested in a
scrap piece of material,  and tightened down (with a 5" allen wrench) to a point
which almost exceeded my full strength,  and didn't strip.  Don't know what
that works out to in ft-lbs,  but it's stinkin' high.  I'm confident that they'll never strip
under normal circumstances,  and when I'm "done" with the engine,  all allens will
be drilled,  and safety wire will be installed.

Another view...  note that all polishing was done before welding.

The welding didn't hurt the polish work,  and doing it beforehand,
ensured a nice job right up to the joint.
This photo also shows the excess material removed from between the log and 
the head,  between the intake ports.

Another close up.  Right clicking on these photos,  and selecting
"view image",  will enlarge the photo another 25-30%.

Here's a shot after all extra material has been removed from the opening.

....And another view.  

I may fill over the top of the weld with some JB Weld,  and grind it all
nice and square,  and do the same to the mating part,  so that there's no issues
with the transition from runner to log.

 Bottom view,  showing the Stromberg updraft mounting flange.

Notice that it's offset to one side.  

This was to make both runners the same length, as mentioned above..