Front bar GT350 from 2016 to 2020: 34mm DIA x 5.7mm wall (1.34 x 0.22 in)
Front bar GT350R from 2016 to 2019: 34mm DIA x 5.7mm wall (1.34 x 0.22 in)
Front bar GT350R 2020: 34mm DIA x 4.8mm bonded wall (1.34 x 0.19 in)
Rear bar GT350 from 2016 to 2018: 22.2mm DIA x 3.9mm wall (0.87 x 0.15 in)
Rear bar GT350 from 2019 to 2020: 24mm DIA x 3.6mm wall (0.94 x 0.14 in)
Rear bar GT350R 2016: 22.2mm DIA x 3.9mm wall (0.87 x 0.15 in ) with 8mm (0.31 in) shorter arms than GT350
Rear bar GT350R 2017: 24mm DIA x 3.9mm wall (0.87 x 0.15 in ) with 8mm (0.31 in) shorter arms than GT350
Rear bar GT350R 2018 to 2020: 24mm DIA x 3.6mm wall (0.94 x 0.14 in )
I contacted Ford Performance, here is what they gave me on the M-5490-G track sway bar kit:
Front Bar: 37mm x 5.2MM wall (2 mounting hole)
Rear: 25.2mm x 4.4mm wall, (2 mounting holes)
Grok says:
the 37mm dia. x 5,2mm wall is 15-20% stiffer than the 34mm dia. x 5.7mm wall GT350 front bar
The 25.2 mm dia. x 4.4mm wall is 25 to 30% stiffer than the 24mm dia. x 3.6mm wall.
that is assuming the arm and mounting dimensions are equal.
Take that with a grain of salt, Ai answers are correct about 66% of the time.
I don't know the arm length or hole placement for either bar.