Any kind of cam change without a converter change is really going to hurt low speed performance. Keep a very close eye on the intake closing point of any new cam you look at. four degrees or less added intake closing point will probably not hurt too much, start going beyond that and you had better get some more compression in it and a looser converter. Two items that stand out that will help you are a flat tappet cam and a stroker. The solid cam will allow a more agressive profile and still have a reasonable intake closing point due to the lash.
The stroker will give you the bottom end grunt to really work the stock converter and make it a whole new motor torque wise. Nobody need know about the stroke increase either!
If you start playing with numbers, you can come up with a 9.5 to one combo with flat top pistons, making sure piston to head is inside .035 to .040 . That will help wake up the motor. You have many options. A stroked stock 383 crank (3.54)can use a chev rod and rod bearing in a long rod of 6.7 or 6.8 length, giving you a piston compression height of 1.5 to 1.4. That would allow for a light piston, and really help things out. You would be at 406 cubes, .030 over.
These suggestions may or may not be inside of what you are willing to do, but thought I would throw them out there to give you some ideas.