How do I check for items in a block and then change the block depending on what is in it

I'm trying to make a furnace block that checks what's in its inventory, then changes the block depending on what's inside of it. My current version doesn't work tho

Current code looks like this:
Event trigger (furnace block update tick every 20 ticks)
if item in slot 3 = bowl and item in slot 0 = iron powder
do replace block at xyz with furnace with bowl with iron keep state keep nbt/inventory
else if item in slot 3 = bowl
do replace block at xyz with furnace with bowl keep state keep nbt/inventory
else if item in slot 3 is not bowl
do replace block at xyz with furnace without bowl keep state keep nbt/inventory

The main point of this is to change the model of the furnace depending on what's inside of it, so if there's an easier way tell me