1985 Chevy Truck Engine timing

I just rebuilt my chevy 350. I got it running but ir is backfiring when I accelerate. I'm wondering if it would be cost effective to have a mechanic adjust the timing rather than me buying a timing light and spending time adjusting it.

What is the average price for adjusting the timing? I know there are a lot of variables involved. However I'm almost sure it's a simple timing issue involving the distributor.