I know of 2 methods for heating the manifold...I just asked this question or shall I say I asked which way is better. On your fentons... I believe there are 2 holes ( Plugged ) one on each header,from there your kit will have Tubes that go from your headers to a plate that blocks the stock manifold bottom ( where your single exhaust connected to.) The heated exhaust gases go thru the tube and into the plate and warms the manifold.
The other way is to get a water kit...a plate goes behind your water pump and a tube connects that to another plate under your stock manifold...and another tube takes the water back into the system via heater return hose etc.
Langdons really like the water method....General feedback I got was the heated exhaust work fine and not as cumbersome and leak prone as the water. I was asking about a stock manifold with 1 carb ....I don't know if this applies to a multi-carb setup.
Hope that helps.

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