If your working on a E body Challenger(1970-74) I would look at mounting them up near the radiator core support on the front sub frames so the exhaust pipe would exit the engine compartment in front of the front tires, not behind them Closer to the inter cooler mounting also if it, intercooler, is mounted in front of the radiator
If the intercooler will be air to liquid mounted in the car then the turbo mounted further back will be closer to the intercooler