We have installed the "Custom Roleplay Data" which allows us to use custom models from our resource pack to replace specific in-game models for specific blocks/items that retain NBT data (so, you can't re-model stone/placeable blocks/armor, but items, pumpkin heads, weapons, etc. can be remodeled). We have also installed the datapack ModelApplier which does a better version of it with a UI, and applies any model to any item.

With Custom_Roleplay_Data, users can rename the desired item to the "name" below, and then hold it in their hand and deploy a simple command to turn the object to a custom model:

/trigger CustomModelName

Alternatively, using ModelApplier, you can rename the item to the "Namespace Name" below, then enter the ModelApplier UI either in the pause screen or by hitting G, then holding the item in your main hand, and do the "ModelApplier" button and then choose "Apply Item Model", then enter the menu again and do "SlotApplier" and choose the desired slot. Both steps have to be done in that order for models to work as helmets and armor.

The The below table defines the current available custom models:

Base Item	ID	Name	Namespace Name	Preview	Description
Carved Pumpkin	1	pinball_helmet	teh3l3m3nts:helmet-pinball		JoeHills Demo Pinball Helmet v1
Carved Pumpkin	2	pinball_helmet_2	teh3l3m3nts:helmet-pinball_2		JoeHills Demo Pinball Helmet v2
Carved Pumpkin	3	pinball_scale	teh3l3m3nts:helmet-pinball_scale		JoeHills Demo Pinball Helmet v3 (Scale Model)
Carved Pumpkin	4	gullopolisindustriessign	teh3l3m3nts:sign-gullopolisindustries		Gullopolis Industries Sign
Carved Pumpkin		sign-syntheria-seaport-01-1x1	teh3l3m3nts:sign-syntheria-seaport-01-1x1		Syntheria Seaport Sign 01 (1x1)
Carved Pumpkin		sign-syntheria-seaport-01-2x2	teh3l3m3nts:sign-syntheria-seaport-01-2x2		Syntheria Seaport Sign 01 (2x2)
Carved Pumpkin		helmet-toilet	teh3l3m3nts:helmet-toilet		Skibidi Toilet Helmet
Carved Pumpkin	100	andesite			Block - Andesite
Carved Pumpkin	101	bedrock			Block - Bedrock
Carved Pumpkin	102	blackstone			Block - Blackstone
Carved Pumpkin	103	cobblestone			Block - Cobblestone
Carved Pumpkin	104	deepslate			Block - Deepslate
Carved Pumpkin	105	diorite			Block - Diorite
Carved Pumpkin	106	dirt			Block - Dirt
Carved Pumpkin	107	end_stone			Block - End Stone
Carved Pumpkin	108	granite			Block - Granite
Carved Pumpkin	109	netherrack			Block - Netherrack
Carved Pumpkin	110	obsidian			Block - Obsidian
Carved Pumpkin	111	polished_andesite			Block - Polished Andesite
Carved Pumpkin	112	polished_blackstone			Block - Polished Blackstone
Carved Pumpkin	113	polished_diorite			Block - Polished Diorite
Carved Pumpkin	114	polished_granite			Block - Polished Granite
Carved Pumpkin	115	stone			Block - Stone