I'm with these guys, DSE stuff is top notch in the industry. From reputation to performance. I like the long term support aspect as well. I had one of the first 100 frames in my 69. It was easily one of my favorite aspects of that car.
Take it from a guy that built one of these from scratch. It's addicting and the snow ball gets big quick.
I would opt for an ls or lt and the t56. The engine is just to antiquated for a modern pro touring car. I wouldn't put that tko600 in your tractor.
Good luck with it.