If original poster is looking for originality, I'm surprised nobody has mentioned the solenoid heat shield...
It is my understanding that a little shield was exactly how Pontiac dealt with the heat on long-branch equipped cars, straight from the factory...while it doesn't protect the entire starter, it does protect the solenoid from excessive manifold heat, which is actually the part of the starter most likely to contribute to hot-start problems.
Other excellent solutions to this problem in my mind that have not yet been mentioned, if OP wants to avoid going to a mini (or maybe in addition to going to a mini):
1. Have the manifolds ceramic coated. Available in any color you could dream of...including OEM-looking cast grey. This not only helps them to look perfect forever and protects your investment, it also reduces heat production significantly, protecting the starter and everything else under the hood, and reducing heat transfer thru the firewall.
2. Aftermarket starter wraps, such as this: Starter wrap
3. Another less original, but extremely common and effective mod: Install a remote solenoid ala Ford. The lovely interweb is chock full of wiring diagrams of this little project...
