Waiting for my delivery, I modified your pi3 with the data available from the raspberry foundation and mouser. Will need a reality check once the board is delivered.
`module pi4()

{
// PCB
color("limegreen") difference()
{
hull()
{
translate([-(85-6)/2,-(56-6)/2,0]) cylinder(r=3, h=1.4 );
translate([-(85-6)/2, (56-6)/2,0]) cylinder(r=3, h=1.4 );
translate([ (85-6)/2,-(56-6)/2,0]) cylinder(r=3, h=1.4 );
translate([ (85-6)/2, (56-6)/2,0]) cylinder(r=3, h=1.4 );
}
translate([-85/2+3.5,-49/2,-1]) cylinder(d=2.75, h=3);
translate([-85/2+3.5, 49/2,-1]) cylinder(d=2.75, h=3);
translate([58-85/2+3.5,-49/2,-1]) cylinder(d=2.75, h=3);
translate([58-85/2+3.5, 49/2,-1]) cylinder(d=2.75, h=3);
}

// Header
translate([3.5-85/2+29-10*2.54,49/2-2.54,1.4])
header(20,2);

translate([-85/2,-56/2,1.4])
{
color("silver")
{
// Ethernet
translate([85-19, 45.75-13.5/2,0]) cube([21,16,13.5]);
// USB
translate([85-15, 9-16/2,0]) cube([17,13,16]);
translate([85-15, 27-16/2,0]) cube([17,13,16]);
// USB C
translate([3.5+7.7-8.94/2,-1.5,0]) cube([8.94,8.75,3.16]);
// Mini HDMI
translate([3.5+7.7+14.8-6.5/2,-1.5,0]) cube([6.5,7.5,2.9]);
translate([3.5+7.7+14.8+13.5-6.5/2,-1.5,0]) cube([6.5,7.5,2.9]);
}
color("darkgrey")
{
// Audio
translate([3.5+7.7+14.8+13.5+7+7.5-7/2,-2,0])
{
translate([0,2,0]) cube([7,13,5.6]);
translate([7/2,0,5.6/2])rotate([-90,0,0]) cylinder(d=5.6,h=2);
}
// Display
translate([1.1,(49-22)/2,0]) cube([4,22,5.5]);
// Camera
translate([3.5+7.7+14.8+13.5+7-4/2,1.1,0]) cube([4,22,5.5]);
}
// Micro SD Card
color("silver") translate([0,22,-2.9]) cube([13,14,1.5]);
color("darkgrey") translate([-2.4,23.5,-2.65]) cube([2.4,11,1]);
}
}`