The second gen camaro/firebird subframe is not suitable for your truck. You will have tire fender clearance issues unless you keep the ride height up at the stock height. I would not recommend using that subframe on an AD truck. If you just have to use a subframe then get a rear steer subframe from a first gen camaro or a Nova.
The best solution for IFS on the AD series trucks is an IFS kit. For the $1,400 you get a kit that is easy to install and ADDS value to your truck. It may cost more initally but you will benefit in the end.
Do what you want but having done a subframe on a 54 I know what I have been there and done that.
