Hello all railroaders.

I bought an undecorated Spectrum Doodlebug from the first run many years ago.  I was wondering if anyone could tell me if the new Doodlebug shells can be used on the old Doodlebugs chassis?  If it does fit will Bachmann sell the shells and what would the P/N be for one decorated for the NYC RR?  Any help will be greatly appreciated and thanks for reading.