Customs Manifold heat question

Hello all.

-1938 Chev PU with dipper 235.

I about about to replace some nasty old dual Rochesters with a pair of Weber 34/36 (real Webers). I started doing research and learned that manifold heat would be a good idea.

Note: I have Fenton exhaust and Edelbrock intake.

I was going to fab a plate similar to the kit from Speedway https://www.speedwaymotors.com/GM-L6-Manifold-Heat-Kit-216-235-261-Fenton-Headers,383213.html
The pic has me a little confused.

My question is:
If you were to use a single line from the exhaust manifold into the sealed plate under the intake as shown in the pic on the Speedway page, without having some sort of a vent or some form of flow through the exhaust flow would 'dead head' and wouldnt provide heat to the manifold.

Does the heater plate on the intake need to have a small hole to vent some pressure so you can have positive exhaust flow through? Wouldnt that put exhaust into the engine bay/cab? (and maybe make a tick noise like a blown manifold gasket?).

I also noted that my Fenton headers have a boss/provision in each side. The forward header has a much larger bolt (by memory it looked like it was 5/8") and the rearward header has something like a 3/8"-5-16" plug, both in the same relative location. Were these designed to be used as a p*** through so you would use a line to each header?

Thanks for any advice on this question.




~JH