Hi, i need help with a custom resource pack i'm making.

I wanted to know how do i make the Pumpkin item appear in your inventory/hand/ground as a plain texture (A normal 16x16 flat texture like Paper, and Ingots), but when placed on the player's head I wanted it to look like the pumpkin block.

I was able to make the item in the inventory look 2d with this model:

{
"parent": "builtin/generated",
"textures": {
"layer0": "items/pumpkin"
},


"display": {
"thirdperson": {
"rotation": [ -90, 0, 0 ],
"translation": [ 0, 1, -3 ],
"scale": [ 0.55, 0.55, 0.55 ]
},
"firstperson": {
"rotation": [ 0, -135, 25 ],
"translation": [ 0, 4, 2 ],
"scale": [ 1.7, 1.7, 1.7 ]
}
}
}

("items/pumpkin" is a custom texture that I made)
But with this item model the block doesn't appear on the player's head when wearing it, and i wanted it to appear.

Any ideas on how to do that? Or if it is even possible? I know that there's a "head" display for items, but I don't know how to use it.
Thanks for reading :)
(Sorry if I made any English mistakes, not my native language)