The cheapest way is to get an arm off an 80s full size Ford Van. Mine came from something like an 85 for $6. This has almost exactly the correct minimal drop to clear the frame. The only problem is that it has a tiny hole for the Ford drag link end. This hole must be opened up for the GMs which are MUCH larger using (IIRC) a 7* taper reamer. Not very common, but they can be found, and most any machine shop can do it if you have a friend with access. Without a friend (or some way to borrow the reamer), typical machine shop rates kill the cost advantage.