What is a 67 TNT 440 worth?

I got the car home today. The engine is not original to the car. The casting date is 4-4-68. The RH head has a casting number ending in 028. I've never heard of that number before. The engine has B body magnum exhaust manifolds, but the LH side has a crack. The engine would still be date correct for a late 68 model car.
The car has a 3.23 gear 742 case Sure Grip diff. Cool!