This. I too have an old suburban. I stuck a 5 speed manual transmission in it. Whenever someone is surprised it's a stick I ask "You want to take it for a spin?"
Everyone says yes. Nobody asks about safety features.
The level of acceptable risk for a one-off bit of fun on your own is a lot higher than what you'd want to accept for an everyday commute, or put your kids in.
Mine has the 700R4 in it, and I have to say, I'm spoiled. I do hope to get another squarebody with a stick in it, but I'm going to turn it into a tractor: 292 I6 with a SM465/205. Very reminiscent of a Toyota LC actually, especially since their original I6 was derived from the Chevy I6.
That 700r4/4l60 and the nv1500 ought to have the same length and bellhousing pattern. Should bolt right up as long as it has the same spline count on the output shaft.
Everyone says yes. Nobody asks about safety features.