Guys, I am amazed at this post! This is EXACTLY what I was dealing with yesterday! I was going to start a post today on this very topic.
I had taken the engine cradle and disk brakes out of a 78 Suburban and bolted them into my 70 pickup. Imagine my disappointment when I found the newer towers do not bolt in. The frame on the 70 is a 1/2" shorter than the 78.
I was thinking of using spacers at the top of the towers, but I wasn't sure that was the answer. But it appears to be. I'll figure out what I need for a spacer and just have a chunk of bar the appropriate thickness and cut it to length. Use some grade 8 fasteners and I should be set. My original plan was to bolt the towers at the top and drill new holes at the bottom. I was going to reposition the motor mounts on the towers until everything sat where it needed to be. I don't think this is going to work as the engine sits too high in the engine bay.
Worse yet, I was going to just reuse the old towers from the 70, but I can't find them.
But I prefer the newer motor mounts anyway.
If I get time, I'll go down to the shop and get a pic of what it looks like now.
Later
Mike