Crankshaft
I seen some crankshafts on thunderracing.com for almost $2000 and I called GM and they said $1600, seen some on summitracing.com for $200.
??????????
The only problem is that you have to get the crank align honed to the block, and that will incur more cost.
Either way, you should be putting a bigger crank in it to begin with.
383 crank was 600 My cost. you do the HP math.

