J heads upgrade

Big range, 100 hp is a lot in difference to each other.

300hp? Dead stock OE everything except headers and a 2-1/2 exhaust, muffler of your choice. Upgrade the ignition.
Well, my builder says 400HP no problem, but he hasn't recommended a cam yet so not sure where he's going with this.
I don't think I should cross that bridge until I have the heads figured out.