340 engine id

MH ? did you swap the first 2 letters?
H is 72
M is Mound road plant.
340
R= regular fuel
3833 = Tuesday, January 25, 1972 (date engine assembled)
0001 = 1st engine built that day at that plant (first time I've seen that) guess someone has to be first lol

2 = 1972
b = Hamtramck, MI (car build plant)
462223 last 6 of vin