Re: Tko 500 600 700 ?
I'm running a TKO600 from CC5S (now Hurst Driveline) and am happy -- those guys give very good post-sale support and the kit went in smoothly aside from issues I caused myself (I had some mismatched 68/69 shifter and console parts)
I picked the TKO600 over the TKO500 mostly because I like the 1/2 gear split better on the 600 (less RPM drop) but the higher torque rating for small incremental price also helped sway me.
With a 3.55 rear, that 3.27 1st is going result in a pretty aggressive 1st gear that will run out of revs quick (25mph ~= 4000 RPM). It'll be fun, but I'd be surprised if you can hook up with all that gear. By comparison, the TKO600's 2.87 1st would be at ~30mph at 4k in 1st and should still be enough gear for you to smoke em with a 383...
Sooo -- I vote TKO600 from the vendor of your choice.