[MARKDTN]

If you remove late LT1 there are basically 2 1/2 bolt patterns for SB Chevy intakes.

Style 1-1955-1986 they are all the same with inner bolts at the same angle as the outers. This also continued with the "Targetmaster" 350 crate engines to the end and aluminum heads on Corvettes until 1991. Intakes through 1968 have provisions for oil fill in the front of the intake. There are factory aluminum and cast iron versions to fit 2bbl, Holley, Q-jet, and early 4-bbl carbs (and early mechanical fuel injection as well as Tuned Port EFI).

Style 1 1/2-1987-1995 center valve cover bolt heads have the same pattern but the center bolts on each side are vertical instead of at an angle with the rest. Crate engines with center bolt (non-Vortec) valve cover heads also have this pattern. There are factory aluminum and maybe cast iron versions to fit Q-jet and TBI (as well as F-body Tuned Port EFI).

I am told that you can go back and forth with these with a wedge washer and hogging out the center holes but I have not personally done one.

Style 2-1996-2000 Vortec heads have a unique pattern with all vertical bolts. The only factory intake is plastic for Vortec EFI.