When I rebuilt my Cleveland I had to bore it 30 over. The machine shop I used was really aware of the cleveland having thin bores. He sonic tested each cylinder to find the thin spots. In my case he told me I can bore it to 40 over but that's it. If I ever need to rebuild my engine again and 40 over is not enough I will be looking for a stout aftermarket block.
I recommend you sonic test the bores to be sure.
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.