is this possible to switch the heads?

no

Nope.. no where near close

theres s series and A series heads they dont match up.

This has been explained before but the 4ag 20v head is an A series head the 5sfe ,3sgte, 3sge, etc are all S series

so in short if you want to use the 20v head you can only use the stock 4ag bottom or 7afe bottom

if you have a 5sfe (gt celica) in your car and want to swap heads look for the topic 5sgte

actually the 20v just has a performance head, G series. F series is the fuel efficient head.

The S and the A just represent the block (3s, 5s)(4a, 7a). Im assuming were talking about the silvertop.
If you were to make a 20 valve "5sfe" it would really be a 5sge. There wouldnt be much of a performance gain in doing this unless you turboed anyways, and even after that it would just be cheaper and easier to do a 3sgte swap. A 20 valve 4age isnt even that much better than a High Comp 4age. But it would be interesting to see a 20 valve 5sge or gte or gze. Even though it would be a PITA, i would still like to see it

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the S series has there own G head (3sge and 3sgte heads)
the A series has its own also (4age 20v black or silver, big port or small port)

furthermore these to heads dont have the same cooling ports so just slaping a 4ag 20v head on a a 5sfe wont come anywhere near close to lining up

thats why i refered to the block series A and S

also this to anyone who wants to swap heads if you dont want to search or do the research then leave your motor alone