I would check where the joint is between the bbl tubes & the block prior to doing a lot of filing on it. It may just be put together somewhat like Pieper's original patent. If so the bbls may not step down inside the block but have a slight taper & insert in the block from the rear. If you filed the block down to a feather edge the block could lose its integrity.


Miller/TN
I Didn't Say Everything I Said, Yogi Berra