Is this a 383?

[SLDPULR]

So I started to tear down my motor today to get ready to go to the machine shop. I have been trying to read up on motors as much as possible over the past few weeks. I pulled the motor and to my surprise its a 4 bolt main 010 020 block so that is good news. They part that is confusing me is that the 400 crank is externally balanced and my crank had a harmonic balancer on it. So does this mean that it may already be a 383? I have tried to search for this info but I have not had any luck. The motor ran good when I started to tear down the truck but I wanted to go with a 383 over the 350 for a little more torque. I looked and didn't see any spots where the block was ground down to clear the connecting rods. Do they make a externally balanced 350 or is my thought process completely wrong. What do I need to look for? I do not want to pull the main caps if it is already a 383. Please let me know. Thanks!

I pulled off the balancer and pullys before I took this picture.