its not that hard, just paste this script inside the grass block blockstate, and dont make any model fit into the directory.

{
"variants": {
"": [
{ "model": "block/grass_block", "weight": 140000 },
{ "model": "?????????????", "weight": 112320 },
{ "model": "blockWHAT11!", "weight": 10 }
]
}
}