The Stovebolt Site Forums The Shop Area The HiPo Shop 1952 3600 motor and possible frame swap

I see that your new frame has a pretty high hump in the rear, so understand the height issue with the cab and bed.

The original cab was mounted in only 4 corners. You could use your wider mounts but you'd probably want to install additional bolts just outboard of the transmission cover unless you tied both mounts together. Note that the cab cross supports there are thinner than where the original bolts are, so you'd probably need to fabricate your mount extension to accommodate that. But I don't think there's a need for additional bolts thru the floor as long as you have room for a cross member tying the two mounts together.

Here's another photo showing what I mean about tying the two mounts together.

[on edit] Yes, it should be C-channel shaped both on the vertical section and where the bolts would go through. I don't think you'd need more than one gusset (the triangular piece) to stiffen up the piece tying the two mounts together. I would use either angle iron or c-channel with the opening downward for that tie piece.