Big Block Suspension Question

My first question to you would be what do you hope to gain by changing to coilovers? There's nothing wrong with torsion bars- just get some nice fat ones, over 1", and a decent anti-sway bar. The only thing to be gained in your instance by coilovers would be a bit more room for header clearance. Not worth the investment, IMO.
Very big weight difference with a complete tubular K-member with a rack and coil overs would be the magor gain. I went with AJE for a light weight drag car. HDK would be the prefered dual purpose due to strength. My street Demon will be all factory suspension. Remember the stiffer the bars the more push you'll have in turns. You need to transfer weight to the outside on entry and exit . The weaker the bar the looser the car will be.