Anyone know this? 5.7 into a 81 truck

Unless TTI or Street and Performance has mounts for that application, you're pretty much on your on to make some. As far as putting a NAG1 in a truck? RUN FORREST.......RUN!! Unless you want to put anti-lock brakes on the truck to get it to work right, I'd forget it. The anti-lock sensors are where a NAG1 gets readings to figure out how fast you're going....and when and how to shift gears. A 545RFE would be a much better choice for a pickup truck, and the factory computer for your 5.7 can be flashed to make it work. Good luck.