Originally Posted by LAS97GT
Get ahead of the game. Cobras have hardened internals already. Costs about 3K to upgrade internals. Maybe more. Gaskets, bearings, man hours. So on.
Pre-'03 Cobras "only" had forged cranks. The rods are still powdered metal and the pistons are still hypereutectic. To the OP, it really depends on what your power goals are. If you'd be fine with ~290rwhp then you can just do a PI heads/cams/intake manifold swap, maybe have the heads machined down a bit to bump the compression further, full bolt-ons, and 4.10s. That would be a nice little setup for a couple thousand. Of course I would rather have the Cobra ('96-'98 Cobras are my favorite modern Mustangs), but that is an option.