If I'm not mistaken dosent this get to up around 429 cubic inches ( depending on bore of course) ? I think this is what Larry Sheppard has been doing , and these things are monsters!
The 'J ' castings are noted for cracking between the valves, if they are overheated. The "X" casting was a better peice. and is considered the best factory production head, and always has been.
If it's a clearance issue your having, you can use a mini starter from a newer vehicle like a 95 Dakota with a 5.2 liter (318) engine, If you have an Autozone near you or some major chain, there fairly cheap.