When I installed the 351w in my car back in the day, I just had long tube headers and some 90 degree turn downs from the auto parts store. I drove it like that a week or two while I saved up for the exhaust. As long as you aren't sitting in the driveway idling for 30 minutes or revving it to 4k RPM, its not that obnoxious.
It was silly riding to class. Just idling through the parking garage without giving it any throttle, it was setting off car alarms. But that was just it being an enclosed concrete box. Outside and in the drive way, it wasn't that bad.