The 64 1/2 ton originally came with a 230. Best way to get a positive id is to get the casting number off the passenger side of the block. the 230/250 series it was located on the lower portion, about halfway back. Earlier engines had the casting number in the area of the starter. Go to
www.inliners.org to the casting # section to look it up.
If it is the later series engine, it won't fit your truck without different motor mounts. The later engines were smaller than the old 235/261.
