Ah, yes the $2500 Chevelle.
There were 3 six cyl engines offered in that car:
-194 cid, 120 hp@4400 rpm, 177 ft. lbs @2400 rpm
-230 cid 140....@4400....... 220..........@1600
-230 cid 155....@4400....... 215..........@2000
Externally they looked pretty much the same. They all had the same piston stroke, the 194 had a 3.565 inch piston bore. The 230 had a 3.875 bore
The two 230 engines used a different camshaft to get the different power specs. I am not sure if the valves themselves were different.
My guess is that if you have an automatic transmission, it will have the 155 hp version. A standard transmission car probably has the lower powered 230, but might have the 194.