Modifications to Offenhauser 1 1/2 carb spacer Thermoquad to Holley pattern ?

'Neccessity is the mother of invention'

I would find a new mother......

Seriously, your best bet is get a 3/4-1" thick piece of alum & make your own spacer/adapter to suit that intake. I have done this myself. You will probably lose a little air flow, but may not be a problem depending on the combo.