/6 Starter Problem

Your problem in NOT likely that you "need more torque." It is FAR more likely that you simply have something wrong that needs fixed, and 'it might be" it could be the starter

You need to load test the battery or have it tested. I'm talking about a high current LOAD tester, not some toy you can hold in one hand

You need to check for voltage drop in the battery cables and connections.

And if that is all OK replace the starter. Mid 90's Dakota/ RAM starters seem to be a popular replacement. They are smaller and much more efficient than the older "wound field" original starters.