like URO said, in a 4X4 HP isnt likely what your after,low speed torque is more likely what you need. Horsepower is the result of torque +RPM...Im guessing you dont plan to see alot of RPM.
one of the cheapest ways is with longer stroke, might be better off with a 350, or 400, or a cross bred 383 for your application.
If your set on buildin the 327than you want to try to gain HP without sacraficing anymore torque at low speed than necessary, high velocity heads , like Vortecs, low rpm cam, long tube headers, dual plain intake , small cfm or spread bore carb, good ignition, etc.