Crate Engine Recommendation

As many of you know I am restoring a 1970 Thunderbird with the 429 Thunderjet in it. After messing with this engine for the last few days and talking to a couple of different folks (one who restores and races old mustangs, darts, challengers, etc) he recommended me dropping a crate engine in this car. I have put oil and diesel down the spark plug holes of the original engine and tried to free up the pistons.... not happening. The mechanic helping me, seems to think that more than the pistons are locked up. What would ya'll recommend? I would like to stay with the 429 Thunderjet style to try and match the car of that time. Any recommendations of who to contact or where to start looking for such an engine? Also my buddy that has restored a bunch of cars, recommended trying to find a fuel injection kit for it. Any recommendations here?