I built a mild LA/Magnum hybrid 360, and an A500 for my 78 Fury (same as your 73 underneath). The trans went in with ease and only had to grind one casting rib off of the case and modify my existing crossmember. I'm using pressure switches from PATC, and a factory GM vacuum switch. The trans swap alone was WELL WORTH IT. It gets unreal gas mileage for what it is (well over 20mpg) once i set the Thermo-Quad up right, cruises 80+ mph with ease with 3.55s, and will fry the tires for as long as you want it to (3.9 converter and 2.74 first gear). I'll never run anything else behind a small block again.