1979-1996 F700 & F800 commercial trucks with the gasoline burning 429 engine. Although the 370 gas motor has the same stroke crank, it is almost surely always a cast version of the crankshaft. (Just checked out a local commercal truck dismantler, and EVERY 370 crank they had in the rack was cast.)
The forged version has the following number stamped on it: D9TE-6303-AA (suffix may also be "BA," or just an "A." I think
.) I have seen a few that were produced in the early nineties, and I think the number was F2TE-6303-BA. They can be confirmed the forged version of the crank by this number or also by the wide parting line, as shown in the photos below:
They are made of 1075 steel and are plenty strong for the same reason that all production 385 Series cranks are strong: that immense amount of journal overlap
. Here is an engineering drawing that depicts structural integrity by way of the journal overlap of the 429 cranks (all
429 cranks, cast or forged), the top circle representing the 2.500" rod throw and the lower circle representing the 3.000" main journal. This particular drawing is with the 429's 3.59" stroke:
Note the amount of overlap area (a whopping 1.371 sq in) and that the overlap's width is .955" at its widest cross section. Try THAT with a chebby!