Slant 6 mod's

You can use the "mini starter" from Magnum engines, ~$50 rebuilt or $10 used at junkyard (RAM trucks, Jeep's). Search ebay. Half the weight and size and sounds better.

A cam change would be the place to start to get higher horsepower. A higher lift cam will make the engine idle worse and have less torque at low rpm, but will bring on the power if you scream the engine (high rpm). However, to be effective, a high-lift cam needs good air breathing, i.e. large intake, ported heads, and free-flowing exhaust.

A cam change is medium difficulty and perhaps a good place to start on engine mod.s. You may have to remove the grill, but if that worries you, you need to get a manual and just jump in. However, if you plan to re-ring or change pistons, might be smarter to remove the engine and do it all at once. Maybe remove the tranny too for a rebuild, since almost as easy as taking out the engine alone.