Just use a system of honesty... its obvious if a car has run a time or not, others have generally seen it.
The LS1 system is a success. Someone put a thread in Performance, make it a sticky, lock it (to avoid postwhoring) and add the times to it (Through email or what not).
As for format, just use something similar to the LS1 i.e.
1 - Morgs - R32 GTS4 - 10.3 @ 140mph - RB26, T51 SPL, street tyres
and so forth