Do you have a budget to stay under? Are you going to be performing some or all of the work yourself? One way to make great power, and not too many Mustang guys go this way, but go with a 96-98 Cobra motor. The B heads flow amazing, (and there frequently are ported sets going for $1k to $1500 on the internet.) You can often pick up Shortblocks for cheap, or build one using the stock block in your GT. I have been looking into doing a B headed 4v when I build a Fox sometime down the road..
