[Mgs] mgb crankshaft part numbers

[jevans at mydb3.com]

Looks like I may need a different crankshaft for my 1977 MGB, with an
"18V" engine.  I have a spare - origin unknown - stamped with these
numbers on one of the throws:  12H4198 on one and HH1 on another.  Also, a
very clear Leyland logo.  Can't seem to find an online listing of Leyland
engine part numbers...can anyone decipher this for me as to original
installation?
Jim Evans, Chicago
P.S. If you can answer the question asked, please do...otherwise, I have
no need for uninformed, shoot-from-the hip speculation or useless advice.