360 or 390 auto barrel bore

I have bought a ‘77 automatic engine stripped to bare parts but no piston. The barrel bore “looks” big ? What should the bore size of a 360 and a 390 be assuming the barrel was standard ? I am wondering if I have a 360 bottom (as the numbers match) but a 390 barrel and head ??

Thanks in advance !

http://www.huskyclub.com/piston.htm
Link to piston sizes, I also believe the 390 has a longer stroke

Cheers for the link.......I’ll need to look at the stroke now too.....

360 barrel has 8 fins, 390 barrel has 9 fins.
They also look different from the side view.

Cheers !

The 360 has a divided exhaust port, meaning two holes with metal between them. I believe the 390 is similar to the 420 with just one port for the exhaust.