Dave
Two points of interest:
If your use the 1919 Valuation map numbers with MP 281 at1474 + 91 and MP 330 is at 4064 + 22 and then extend the miles from MP 281. You get MP 330 at 4062 + 11 or about or 211 ft off.
Also in some 1956 photos you can see the MP about 10 to15ft down the slope from its present position. As I understand it the MP was moved up closer to the track about 15 years ago so it could be seen more clearly.
Jim