Im looking at a set of 18x8" rims with a PCD of 5x114.3 and ET+42~+45

Would these fit on a 3rd Gen TF magna?

They would fit man.
Not sure about the offset though, it would be very close to the standard.
And wouldn't be a problem.

I've had two sets of 18s on my car:

Current Set
18 x 8
+35mm offset

Previous Set
18 x 7.5
+45mm offset

Both fit fine without any issues
I think you'll be right mate

Awesome!
Cheers for the help guys!

maybe get a test fit first?
i've got 18x8's and my offset is +38 and the front tyres sit flush with the guard

my last rims were 18x8 with a 45 offset

no issues