Some things to think about.
1st. The Trans Am clip is too wide for an AD truck. In order to keep the tires inside the fenders you'll have to order rims with a great deal of back spacing. $$$$
2nd. Although it may sound like a good deal, by the time you replace the ball joints, rubber parts, rebuild the brakes etc it's going to cost you almost as much as the TCI suspension.
3rd. You may save some money up front but there will be a whole lot of labor later on trying to hang all your front-end sheet metal back on a frame that wasn't made for it. Also if you choose to narrow the clip so the tires will fit you now have to add new motor mounts etc since the stock units will be too narrow.
A lot of people seem to think that doing a clip saves a lot but it's a fallacy. What you save in money gets eaten up buying special parts to make everything work together. If it doesn't then your spending hours and hours figuring how to get all your sheet metal mounted correctly and aligning properly.
Go with the crossmember. If you have to use a clip go with a Nova, at least that won't be too wide.