Just crunched some numbers here and came up with>

@423hp/3700
60 Foot E.T. : 1.67
1/8 Mile E.T. : 7.57
1/8 Mile Trap Speed : 89.76
1/4 Mile E.T. : 12.00
1/4 Mile Trap Speed : 112

@493hp/3700=
60 Foot E.T. : 1.59
1/8 Mile E.T. : 7.20
1/8 Mile Trap Speed : 94.46
1/4 Mile E.T. : 11.40
1/4 Mile Trap Speed : 117

So around 70hp more is needed, depending on what you have now and how you run it...ported heads/cam/carb improvements would certainly help towards that and then perhaps a look at the l/spring & shock set up depending on results...my2c.