FWIW, when I started my conversion, all I bought from JTR (AKA Stealth Conversions)was the setback plates and spacers.  They aren't that expensive and to make them myself, even though a simple task, would take time, which it just wasn't worth.  The trans mount, radiator support etc I made myself.  For as simple as the JTR units were, they did seem quite expensive and I didn't agree with the design.  All the other misc. items, like radiator, cables etc I picked up at the JYs.  If I remember right, JTR wanted about $200+ for a Camaro Radiator, got a good one from the JY for $30 
Tim