Overdrive ??????

[Luis 67RS]

I have a high HP rebuilt TH350 with all new tci parts. I want to run an overdrive and have been reading up on gear vendors under/over. would I be better off with a gear vendors or by installing a 4l60e in my 67 Camaro? I'm pushing approximately 570 hp from my sbc. I use it for street/ strip action and running 3.91 rear gears.