The perceived easiest would probably be to use the Meriah fans (straight bolt in replacement) or an alternative is to change the exisitng fan blades to a Ford Cortina fan that has 8 (I think) blades for increased air flow. However, both are becoming hard to come by and the Flex-a-lite dual fans are around $220 new, so personally I'd upgrade once and for all to a modern Flex-a-lite system.
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.