If you have a good machine shop near you, see what they will charge to build you an engine. If you can find a rebuildable engine out of a 70's Chevy car, you might even score an SB400. Lot's of torque in those puppies. They are the prefered engine for dirt track racers.
If you don't want the hassle of rebuilding, you can try Jasper Engines. Their address is jasperengines.com. I've put them in and they can sell you whatever you want on performance.
As for fuel injection, you can adapt a newer engine or go the aftermarket route. Edelbrock has a bolt on system for street rods that come complete. It bolts on in place of your old intake. This way, you buy a long block rebuild, the Edelbrock system and drop it in.
Of course, this would be a good time to clean and detail your engine bay and maybe clean the wiring up a bit with some wire looms.