F0301PX tells it was assembled in Flint and with a non intergral head the 1 in that sequence makes it a 1971. There were no 230 - 250 in 1961 and in 1981 they had the intergral head. PX is the code that will tell you what trans and other engine options it may have had.
Techno babble aside the easiest way to distinguish the 194, 230, 250, 292 from a 235 or 261 is by the number of bolts on the valve cover. The 194 to 292 all had 7 bolts. A 235 or 261 has 4. Count the holes and order the headers.
