Subframe connectors are an awesome idea if you don't have them already. I notice you have a 5 speed and don't mention anything about a shifter; thought about that?
I have Griggs SFCs and a Steeda Tri-Ax, I like them both and would strongly recommend them.
Ide do the subframes, or a short throw shifter next.
in my opinion just about any mod is worth the money, if you plan on keeping your car for a long time, start working on the suspension, K-member, LCA's etc.
i have a short throw already and the suspension is already done. i just found out that my extra plenum was ported, i just need to figure out my winter plans for the mustang before i buy the paint that i need