Hi Gene, I am new to the classic parts page and was searching the posts for casting number info and found an interesting thread. You posted some information about blocks and heads for a 1955 1st series and I was wondering if you could help me with a question too. I have two 1st series 55 chevy trucks with 235 engines. One is a 4spd and the other is a hydramatic. Both have the same block # 3835911. The 4spd head has a casting # 3835913 and the hydramatic has a casting# 3836848. I want to restore the 55 with the hydramatic tranny to 100% original so I want to make sure I have the original block and head that would have been assembled on the line in the factory. Can you tell me which set would be original for the 55 1st series or if both work what you would recommend for best quality and performance? THanks, Chuck