Attached models will fit Holley Sniper & Terminator TBI units.  You will need to modify the OpenSCAD code to make a taller hat for regular carburetors.

This is very easy to do.  Just change the BASIC PARAMETERS in the OpenSCAD code to meet your needs.

// BASIC PARAMETERS

ccBaseDiameter = 5.125 * 25.4;  // 5 1/8" base
ccHeight = 1 * 25.4;                      // 1" tall
ccStudDiameter = 1/4 * 25.4;     // ¼" stud
ccThickness = 4;

Recommended slicer settings:
6 perimeters
4 bottom/top layers
5mm brim
15% Grid infill

I generated a cap (no stud hole) by setting the ccHeight to 7/16 * 25.4 and the ccStudDiameter to 0 * 25.4.

Enjoy!