Diassemble and clean all grounds to the starter and block to frame and frame to battery. I mean actaully clean them wether they look okay or not. Make sure your wire size is big enough and that will sometimes correct the problem. Usually it's a starter problem though. Cna you crank the engine with out the ignition ON, is it better?
If you've got time, there's a lot of information on this very subject in the electrical section, including much of it involving me and my Olds. I ended up installing a remote solenoid on my Olds after checking everything out on my system and making sure those items weren't the problem. So, do a search if you want, read and get back with us as you work your car with any questions you may have. Let us know how it goes!
Try a Heat shield, Wrap the right header down and as far out the bottom as possible, move any possible air flow restrictions and heat sources (like sagging heater hoses)
In extreme Cases of no heat evacuation, I have used like a 3 inch diameter dryer vent install kit, mounted it to the Front of the radiator support and directed the chrome collapsible metal hose right on the starter. This provide some good airflow and things run real cooler..
The last resort or first, is remote starter system using a Ford type solenoid.