One more vote for weld in. I have a conv. and the best mod I will have ever done is subframes. Bought mine from Thunderbolt Motorsports in Miami. Steeda 4130's w/ crossbrace for $100 (he auctions them off from Ebay).
In fact I think he's registered on here under Gator_Bill.
They work great!
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Green '94 GT conv. -- K&N filter charger, FMS 9mm wires, Accel hipo cap/rotor, 180* thermo, 14* timing, PRO 5.0 w/ stock handle, off road H-pipe in front of 2 chamber flow's, Steeda subframe connectors w/ crossbrace, stock, stock, stock, yeah and that's stock too.
My 'Stang