you just need a strong clutch Many raceclutches and what the put in forexample those 800-1000 hp skylines and supras are so strong that they dont mind getting flatshifted
And yes you can have that.. comes as a setting with the G25 i believe
Montoya is not flatshifting, he's doing clutchless shifts, which is possible in LFS (though needs a much more precise revmatching than in reality, afaik).
Say you have the following gear setup that at 50mph
2nd = 5000rpm
3rd = 4000rpm
4th = 3000rpm
You should be able to change into 3rd WITHOUT the clutch if you rev the engine at 4000rpm at 50mph. You can change to 4th without clutch at 3000rpm
That is rev matching. You blip the revs to the required rpm to allow smooth gear changes. Normally you would use the clutch but matching will keep the car in balance. You do the matching instead of the syncromesh