B&A Tank engines the 300's a few quesions

Hi
I have a question about the B&A tank engines the D2a's and D2b's ... When these locomotives were rebuilt by Lima locomotives works between 1929 to 1931 , What was done ?
My second question is dealing with the D2b's 310 -317 in what photo's I can find these locomotives did retain their Walschaerts Valve gear , and did not get Baker valve valve gear in their rebuilt , why ??
My next question , Why weren't they rebuilt , West Springfield instead of Lima Ohio ?
My next question dealing with the boilers , the were Saturated Steam before rebuilt , did the locomotives receive new boilers or just new front and back flue sheets , once returned to the B&A the engine were Superheated instead of Saturated Steam ... thank you Pat

From a few early photos I've seen, tank engines 300-309 (orig. 1250-1509) were not equipped with Walschaerts valve gear, but some earlier type, possibly Richardson. This might explain why they received Baker valve gear and 310-317 didn't.
There are a large number of B&A steam photos at:
https://sites.google.com/site/bostonalbanyrailroad/home

Hi NYC Dave
Thank you for the reply , the eariler engine had Stevenson valve gear , as built , ,, Pat