Call up Swartz Chassis and order one of their custom frame/big brake/ford 9" chassis kits. Base chassis is around $10K but you will have to add options for big brakes. I would bet you could spend around 16K for the chassis and it will handle like it's on rails.
Buy an LS 6.2L from Summit making 625HP for around 10K. Get the car painted with new interior. You will be able to drive that car on 2000 miles trips and ride in style/comfort. No more plugs fouling after 6000 miles, terrible gas mileage and old technology. Keep the 348 if you ever want to sell it to someone that cares about stock specs.
Go LS and never look back.
1968 Impala SS Fastback 383 stroker