Spark plug for 1/4 mile, head modified

[Luis911]

My mustang is 1988, Speed density, 5 speed.
TPS=0.985 V and RPM=1000 (Idle)
I ran 1/4 mile (alt.=7,284 ft =2.22 km)
With spark plug Motorcraft ASF 42C 0.45 Elapse Time = 18.8 sec.
With spark plug Champion BLY15 and 0.33 plg Elapsed Time =17.2 sec.

What timing I set or what do I do for best performance???
The idle=1000 rpm is ok???? I can't adjust between 750-800 rpm, I know the head are modified.

Thanks

 

[Luis911]

any answer or opinion??????

BYeeeee

 

[86bluecobra]

I would be running whatever doesn't ping. At that alt you will be running richer. You should be able to get a fair bit of timing into it.