Hi Gary,
Look along the edge of the engine oil pan flange under the fuel transfer pump.
The serial number should be stamped on the vertical edge of the casting.
The #14 grader is to late a model and does not interchange but a #12 model 8T, 80C (Direct start), 70D (In seat pony start), or a 71D (don't remember starting) would all be candidates for parts along with the 8U/9U series plus D318 industrial engines.
As far as pony crankshafts, I show the 5F8405 crankshaft as interchangeable with the 4R/5R D6, 8U/9U and 20A-977 and also the 9K/7T graders would be candidates.