picked up a set of GT40 heads off a 95 cobra for $350 shipped...normally they go for $400ish without shipping, and i got a set of 1.7 rockers too that i can sell and make back almost half my money
differences are...
bigger valves. 1.78int/1.46exh on the stock heads, 1.84/1.54 on the GT40s.
bigger intake ports.
slightly bigger exhaust ports.
along with some improved runners. what this equates to, stock for stock...well heres the flow numbers.
Stock heads
Intake @ .xxx lift
.100 55.4
.200 101.3
.300 140.9
.400 150.8
.500 164.6
Exhaust
.100 42
.200 78.9
.300 102.4
.400 110.8
.500 114.2
GT40 heads
Intake
.100 54
.200 107
.300 157
.400 183
.500 192
Exhaust
.100 47
.200 94
.300 119
.400 128
.500 128
im gonna do a little work on the GT40s with some help from an online how-to and get a little more out of them, but they should be good for a few HP, especially with the blower on there.