[cobrashoch]

Jtann- they are called sub frame connectors. Get the type that ties both sides of the frame rails together back and forth and sideways. On this type usially you will have to run some bolts up through the floorboards. Just tying the front to rear rail together helps a drag launch only. The type that connects side to side will help (considerably but not totally) prevent the roof from warping from torque wrap. The side connecting type also will help your cars torsional stiffness for road or street work. I would also use polygraphite bushings ($200) and give Eaton spring, custom racing spring division a call, to make you a set of custom springs that will bolt right up to that Mustang, that can take the horsepower.($300) All good money spent if you are going to play with that thing using a 385 engine. The weld up type of connectors are the best type, but the bolt up type will work too. The type that has you drilling holes in the subframes can promote rusting in the holes and weaken the subframes slightly too boot.
cobrashock