You don't need a coilover suspension conversion. If you're willing to pay $3,500 for one of those, do this and have your ENTIRE car done.
1.06 (or bigger) Firm Feel torsion bars - $355
Tubular UCAs (PST, FFI, etc) $350
Adjustable strut rods (PST SR 14385) $279
Solid tie rod sleeves (PST SAS 440S) $49
LCA boxing plate (PST LCAPLTMOP621) $15
Greasable LCA pins (FFI w bushings) $135
Hellwig Sway bars
Tubular front 1 1/8 #55904 $175
Solid rear 3/4 #6907 $237
Afco leaf springs
20231M (121 lb) $320
(or 20231's, 142lb, if you prefer, $340)
1 bushings for shackles
Energy suspension 2-2117G $9
Hotchkis RCD shocks
(RCD-70-56663) $400
Grand total so far is... $2,324
Go ahead and add /6 to 440 mounts $177
A Bergman Auto Delphi power steering box $675
And you're at $3176
Since the brakes were included in that package, add Dr. Diff's 10.95" kit for $445
and now you're at $3,621.
But you've done the suspension on your ENTIRE car. If you really need to compare apples to apples drop the rear springs, rear sway bar, and rear shocks since the coilover kits don't address the rear of the car at all. That puts the total back at $2,864.
I list everything above to compare to the TVS kit, and I think that the above set up would be in the same performance ballpark. The Hotchkis set up has some nice parts, but not everything is needed and some stuff that should be included isn't. Also, I include some of the parts above because with the exception of the lower control arms, all the parts will be NEW, so no concerns about damaged or worn out parts. You could do it cheaper without the new pivots, by rebuilding the stock UCA's etc. But that's my .02. I think a car set up with all the above parts, a good set of tires and a competitive alignment would be in exactly the same ballpark as any of the coilover conversion cars as far as handling is concerned. I know some folks disagree with that, but realistically the average driver or even the occasional weekend track warrior is unlikely to notice much difference at all. You'd really have to put a stop watch to it, and at that point I think tire choice and shock valving would probably play just as big a role.