Here's what I'd do. Marked in yellow. That mimics the original cab mounts on the original frame, just taller. Maybe weld a stringer between them with some diagonal gussets to minimize side sway. Put a rubber pad (simulated in red) on top of the bracket where the original cab bolt is. Depending on the frame shape, either thru-bolt thru the web of the frame or weld to the web (never weld on the flanges of a frame.) On the rear, I'd use the original style cab shackles to allow for flexibility and fab a similar mount to what I've shown but with the top part vertical (although you could bolt the lower cab shackle brackets to a horizontal portion of your fabricated bracket. Again, tie them together side to side with some corner bracing to minimize flex.
A question. Is it really necessary to mount the cab that much higher above the frame?
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
