[Varyon]

I had to do some of this for my Vehicles->Spaceships conversion. Up through TL 4, the tech levels are the same. 3e's "early TL 5" (which is a thing in Vehicles) is 4e TL 5, while 3e's late TL 5 and TL 6 are condensed together into 4e's TL 6. 3e TL 7 gets split up into 4e TL 7 and the earlier part of 4e TL 8. Beyond that, things were speculative and are based on different paradigms, but 3e TL 8 matches up decently with later 4e TL 8 and some 4e TL 9. Beyond that, I don't think comparisons between the two are very useful - you'd need to look at each individual piece technology to determine where it fits in the 4e scheme of things.
I should note this is based on a combination of the dates given for the TL's and the way the technologies work in Vehicles, as I have no other 3e books.