250 I6 Stock Manifold help

[72Straight6]

Looking for a little help.

I recently bought my '72 C-10 with a 250 I6. The throttle linkage is attached to the current intake with some 'hardware store bracing'. I have been told I need an Intake Manifold that has a mounting hole that would be 'cast in' to the stock cast iron manifold; then I could attach the throttle linkage to this bolt hole? If you were looking at the manifold (installed) from the top carburetor view, the bolt/mounting hole would be on the side of the intake closer to the firewall.

I have been searching for several weeks, but have only found one that is selling for $200 (seems a bit high). Does anyone have any advice on how/where to find one at a more reasonable price?

Also, looking to find the 'intake attachment' to upgrade to a 2-barrel carb (from my current 1-barrel.

(side note - I am possibly going to switch out my motor from a 250 I6 to a 292 I6, but as far as I know, I am going to need these exact same parts for my upcoming motor project).

Thanks for any & all help!!

Joe