Put a rebuilt long block in 2001 Dodge 318 engine new tune up not missing but idels rough and goes dead when you put it in reverse?

it could be many things but i know my dads truck was doing this and i adjusted the TV (throttle valve) cable that runs to the tranny and it started to smarten up then i checked the plug wires and such and it was number 1 and 4 wires were in the wrong places after he had the cap rotor plugs wires done at a shop so id recomend checking those things the tv cables are simple to adjust just google it and it should come up with something and check your timing is correct it might be dying because it cant keep up rpms when you drop it into gear