like those:
http://www.avouk.com/MotorsportFrameset-84.htm (go to "Universal" and select "Twin / Mono tube", you have the pricing there also)
You can keep the torsion bars and add some softer springs on shocks, or use only the stiffer springs without torsion bars. Depends on what spring rate you are running in the front. I have a 182 CUP front spring and looking for some Express torsion bars, as they are identical to Renault sport Gr.N bars for 1.8 16V and Williams, used in rally. Those from Express are the same as softer Gr.N, with 23.2mm diameter, but there are/were also stiffer for Gr.N, with 24.5mm diameter.
Hope I helped