The front crossmember and frame rails need to be modified to accept the front core support. This is needed to be done to keep the nose ie fenders and hood aligned properly with the cab.
The offset in the frame rails leaves the front frame horns and strut rod crossmember to high for proper fender & hood alignment to the cab. So, to make the modification you need to remove the crossmember.
Crossmember removed, it is riveted to the frame rails, so they need to be cut to remove it and I re-used the original rivet hole to bolt it back into place after it is modified.
Here you can see how I marked the frame horn out where it will need to be cut.
This is the completed frame horn cut and the modified crossmember.
The top of the frame horn needs to be lowered 1.25" x 6" back to get the proper height and clearance of the core support.
Then 1/2 of the top of the rail has to be cut back an additional 4".
I welded the top of the frame horn back into place to make it look good on the 6" section. The crossmember also needs to be cut to give clearance for the radiator lower tank. The crossmember needs to be lowered 2.50", leaving it 1" tall from the bottom rail of the frame. I cut the crossmember the same way I cut the frame horns and welded the top section back to the lower after cutting out 1.25" and just filled in the areas that didn't line up. I also made a small gusset to connect the different heights of the top rail where the 6" & 4" cuts meet.