Help with identifying engine

With the P designation it should be the 10.5, big valve, forged crank engine. The cast crank engines were low compression and didn't require high octane fuel thus no P in the assembly stamping.

G = 1971
M = Mount Road engine assembly plant
340
P = premium fuel (high compression engine)
3548 = as said - Thursday April 15 1971
0045 = 45th engine built that day