If you put this code on your GG1 mdl file:

{
materials = { "vehicle/asset/lights.mtl", },
mesh = "vehicle/asset/lod_0_light_round_white.msh",
transf = { 0.99619472026825, 0, 0.087155744433403, 0, 0, 1.7000000476837, 0, 0, -0.14816476404667, 0, 1.693531036377, 0, 11.279999732971, 0.0099999997764826, 3.2699999809265, 1, },
},

inside of:

lods = {
{
node = {
children = {

the light will work now, i also have converted some AMTRAK stuff for myself from TF1 including some GG1 locomotives.
I hope it helps you.