The holes with the smaller threaded insert are the front of the head where the accesories bolt on and these inserts are blind meaning they are plugged. The rear of the head will require 5/8 coarse thread bolts or cap screws, I bought mine at a local hardware store and added copper washers to endure a good seal.
Head plugs on Flickr - Photo Sharing!
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Paul O
1990 F150 4x4 XLT X-Cab 5.0, 3.55LS, Comp XE264HR-14, Flowtech LT's to 3" single, FRPP Mass Air Conversion, TweecerRT with BE, Innovate LC-1 wideband O2
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