Like I said....if it comes to it. The weld ins are deffinately not the easy way to go... I don't know about the early a-bodies. Call TTI and ask if thier mounts will work on your application. http://www.ttiexhaust.com/ContactUs/ContactUs.htm
The weld in mounts and brackets may need modification. That's why you need your exhaust manifolds / headers (and everything else) in place to check clearences during mock up.