Look again at the site. Langdons does offer the single linkage kit for the holley/webber carbs they sell. $35 for it and $15 for the carb adapter and $75 for the Holley/webber carb.
The Carter/webber is $85.
The air cleaner for it is about $30
The 4bbl offenhauser manifold is typically $230 from Langdons
The 390 Holley 4bbl carb is typically $439 from Speedway
Then add in the manifold gaskets,fuel line, linkage, carb adapter and air cleaner setup costs and you can see this route is not the economical way of doing it.
you can spend $670+ or you can spend about $155 with either route getting better results than a stock 1bbl. Your only limitation is your budget.
In answer to your question on the most economical upgrade: I would suggest going the single 2bbl Holley/webber route. This is the route I'm going with my 194 6cyl in my 64.
As much as I would rather put a 4bbl 390 Holley setup on my engine, I just can't afford that kind of upgrade new.
Either route is nice, but the choice is up to you.
