not sure what to believe with this, dont think we will ever really know
If you look at athletics records over time it seems unlikely that people cant bowl as fast now with better nutrition/sports science etc...
Thomson used to be a javelin thrower and his javelin thrower/catapult action has never been replicated.
So, while athletics records have improved incrementally over time, someone bowling faster than Thommo will likely only be possible when some replicates his unique biomechanics and enormous shoulder strength.
Most of the footage of Thommo on the net is from him in his 30's way after his peak/shoulder reconstruction.
When I saw the Windies fast bowlers live from side on 1980 Boxing Day test, I was staggered that I could not see the ball after it left the hand and by how far back the keeper and slips stood.
With Thommo, the keeper and slips stood even further back.
One thing I do know is that Akhtar, Lee, Tate etc have never given me the impression with the naked eye of being faster than Thommo.
For an over or two, they might be nearly as quick, but Thommo would bowl at their pace for longer and his fastest was like WOW.
I wish he was around now, he would be a sensation.