Hey Richard! I have the Shawmut 2-10-0 too. The real engine the PS&N had did have the longer back porch on the tender, so the MTH model is correct in that respect. The Erie engines seemed to have short end sills, from what I have seen in photographs.
Where did you get the Shawmut caboose? That definitely caught my eye...
"The glorious past, the wonderful future and the crummy now"- Jean Shepherd