The best replacement for t3 t4 is 16g.

The best alternatives to t3 t4 are rated as following:
★★★★★  16g
★★★  t28
★★★  t3
★★★  t25
★★  gt35r
★★  t04e
★★  20g
★★  gt28rs
★★  td05
★  hx35
★  gt30
★  td06
  gt28
  tsh

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Speaking about t3 t4, one probably shouldn't forget about high tsh.

Other search terms related to t3 t4 and their ratings are:
★★★★★ high tsh
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t3 t4
16g
t28